David Fischer, 21, told insidethegames his decision to switch to Bulgaria had cost him any chance of qualifying for the Tokyo 2020 Olympic Games, and also said "the outcome would be very different" if the Austrian Federation (OGV) had a different leadership.

In response, the OGV President Gerhard Peya said Fischer was being "naive" and voiced suspicions over the athlete's whereabouts information provided to testers after he missed four tests in two years.

Austria's national coach Johann Lechner, who was criticised by Fischer on social media, said Fischer was "on the way to destroying his own career".

The rift with the OGV concerns other members of the Fischer family – David's high-achieving sister Sarah, and their father Ewald, a coach who is on the Board of the OGV.

Sarah, an Olympic contender in the 87 kilograms category and a multiple medallist in world and European youth and junior competitions, said she had also been thinking about changing nationality but "right now I'm feeling like it's the last thing to do".

Neither David nor Sarah, 20, who both joined the Austrian Army professional athletes' group, has ever tested positive, and David said that his decision to compete for Bulgaria would result in him being tested more than ever.

Bulgaria, unlike Austria, has a bad historic doping record.

The two are coached by Ewald, a former national record-holder who has a very strained relationship with Peya.

"As a family we were more successful than the whole federation, and I guess that's where the problem started," said David Fischer.

The Fischers were unhappy about comments from within the OGV about doping, and David decided to quit Austria more than a year ago when he heard that a criminal investigation had been carried out – though he did not make his decision public until the past week.

The investigation, which the Fischers say was the result of a tip-off from a senior official of the OGV, was dropped when it failed to find any evidence of wrongdoing.

David missed tests four times when he was travelling back and forth to Bulgaria.

He has a Bulgarian fiancée, speaks the language fluently, and was granted a Bulgarian passport in February.

He did not miss three tests in a year, which could have led to a two-year suspension, but Lechner referred to the missed tests as "doping offences" and sent a message to Ewald Fischer stating "a missed test is a positive test for me".

Gerhard Probst, chair of the Austrian Anti-Doping Legal Commission, told Niederösterreichische Nachrichten – a local newspaper that serves the Fischers' home town of Rohrendorf bei Krems – that it was "nonsense" to equate a missed test with a positive test.

Lechner also pointed out in a statement sent to insidethegames that Ewald Fischer had administered ephedrine to both Sarah and David in training in their teenage years.

That stimulant is not prohibited except in competition and is widely used within weightlifting.

Sport doping is a crime in Austria, and when information was provided to the National Anti-Doping Agency it led to the public prosecutor approving an investigation in the autumn of 2018.

The Fischer family was not aware of the investigation, which lasted months but was dropped when it produced no grounds for prosecution.

Peya denied that anyone at the OGV had tipped off the prosecutor, though the Fischers have a document – seen by insidethegames – which states the source was "a high-ranking OGV official who has been closely following the sporting development of the athlete in question for many years".

"The public prosecutor acts freely, independently and without influence," Peya told insidethegames.

"But when a sportsman is a soldier and paid by the army, the army get more information.

"When a young athlete does not understand he is very naive."

Peya said he had asked Ewald Fischer, as a member of the OGV Board, to provide copies of legal documents sent to him by the prosecutor's office.

"He didn't do that," he said.

"Why should it remain a secret?"

When asked why he thought David Fischer had switched nationality, he said: "Maybe he didn't like the fact that he had been checked several times.

"That can only bother you if you have something to hide."

When David Fischer, already angry about persistent rumours, became aware of the investigation last May he decided he would never compete for Austria again.

He de-registered from the national federation and the Austrian Army professional athletes group, of which Sarah is still a member.

He gave up any hope of qualifying for Tokyo 2020 when he withdrew from competing after the European Championships in April 2019.

Fischer removed himself from ADAMS, the global anti-doping database, in June last year and became ineligible to compete internationally, though he was still a member of the OGV.

"He had no contact with the OGV about a change of nationality," said Peya, who learned on social media that Fischer had been given a Bulgarian passport earlier this year.

Fischer will not be able to compete for his new nation until March 1, 2021.

"I have not responded to the offer of David Fischer in the past weeks via media of €5,000 (£4,500/$5,600) for an early release," said Peya.

"I classify such an offer as a bribe."

Peya pointed out that the Fischer family had done a great deal for their children and that Sarah had achieved great success.

Both David and Sarah had been coached in their formative years by a Bulgarian who, he said, was banned from Austrian clubs and competitions for life by the OGV for a doping offence in 2002.

"This trainer taught the young athletes David and Sarah impossible techniques," he said.

"This technique, practiced by Sarah and David, can hardly be corrected and is not used internationally by anyone.

"Many experienced trainers from different countries have told my national coach that this technique will sooner or later lead to injuries.

"All efforts of our reputable trainers in Austria were unsuccessful."

Sarah Fischer disputes much of this, including the "life ban" for the coach.

"When Sarah was no longer able to exercise, her father gave her amphetamines," said Peya.

"Austria's national coach didn't want that."

On the question of the missed tests, Peya said he had originally thought David had made a mistake, but on checking his whereabouts information after two missed tests he changed his mind.

"Some of the travel routes and times were impossible," said Peya of David's whereabouts data.

"In order to discuss this personally, I asked David to speak to me in the secretariat about his next plans.

"The face-to-face conversation was still nice and I wanted to believe him."

But within days Peya said he learned of another missed test.

Lechner said he took issue with Ewald Fischer's use of stimulants that are prohibited in competition but not in training – especially amphetamines, because of the potential side-effects.

He said he was worried about David's weight gain from 2017 to last year, when he moved up from the 94kg category to 109kg.

"After more than 50 years of experience in weightlifting, it was clear to me that something was wrong," he said.

Lechner explained his concerns to Fischer privately, he said, making it clear that he was not accusing him of "taking any prohibited substances" but that his main aim was to protect clean athletes.

Lechner was disappointed that Fischer was "playing hide-and-seek" with his whereabouts information and missed another test shortly after the private conversation.

"Who is hiding? Only someone who has something to hide," said Lechner, who no longer wanted Fischer in his training group.

He felt insulted by Fischer's criticism of him on social media, he said.

"The charge that I would destroy his career – I have no interest in destroying his career, but it looks like he's on the best way to doing it himself," he said.

"It is always easier to blame others and not to look for the mistakes in yourself.

"For me, the responsibility for the misery lies with his coaches, and his father Ewald is one of them."

Sarah Fischer said the Bulgarian coach had not been banned for life.

"How was he banned if he was hired from a weightlifting club in Austria, SK Voest Linz, till 2010?" she said.

As for her technique, she added: "I will not say it's the best but if it's so bad how did I win all my 27 international medals?

"Never once did a coach from Austria help me to change my technique, and I don't know why the President is talking bad about me now.

"Yes, I did take amphetamines but it's allowed in training so I don't see a problem with it."

David Fischer first visited Bulgaria in 2010, as a 10-year-old, and has trained there on many visits.

His father's contacts throughout Europe helped him to find a club and a coach there, in Sliven, and as well as learning the language and making many friends in the Bulgarian national team he met his future wife Nazik, a former acrobat.

After training at home during the COVID-19 lockdown, Sarah has now joined David in Bulgaria for a training camp that will run until late August.

She has also trained in Armenia before – helped by Sargis Martirosjan, the former Armenia lifter who now competes for Austria, where he has lived for years.

"It's just a very different feeling to train in other countries, in countries where weightlifting is a national sport, not like in Austria where I'm most of the time alone in training," said Sarah.

"It's hard to say if I will ever change nation.

"Of course since my brother did change I'm thinking a lot about doing it too, but as things are right now, I'm feeling like it's the last thing to do."

David said: "I think if other people had something to say in all of this, the outcome would be very different."

Austria famously lost a top weightlifter to a nationality switch before.

Matthias Steiner, who competed for his native Austria until 2005, decided to compete for Germany after a dispute over who should coach him.

He won the super-heavyweight gold medal at the Beijing 2008 Olympic Games.