Pitner was one of two umpires, who it was claimed were secretly banned by the International Tennis Federation (ITF) for betting offences.

He received a 12-month sanction in August 2015, having been found to have sent details about a player's well-being to a coach during a tournament.

It was also alleged he had logged on to a betting account from which bets were placed on tennis matches.

It followed an investigation by the Tennis Integrity Unit (TIU).

They also banned Kazakhstan's Kirill Parfenov for life in February 2015 after finding him guilty of speaking to another official on Facebook in a bid to manipulate the scoring of matches.

Four more umpires are also currently under investigation, according to the Guardian, with the ITF facing allegations that it has "covered up" the offences.

Pitner was approved to officiate at the 2015 US Open, despite being suspended after he was added to the banned list the day before qualifying for the tournament began.

“After learning within the last 24 hours that an official on the ‘do not credential’ list may have worked at the 2015 US Open as a linesman, the USTA immediately investigated the claim,” the USTA told the Guardian.

“The USTA was shocked to find that this was in fact the case.

“As we have now determined, Denis Pitner had been approved to work the US Open as a linesman on 13 July.

“The USTA was notified that Mr Pitner was placed on the ‘do not credential’ list on 24 August.

“Mr Pitner had already picked up his credential prior to the USTA being notified.

“Due to a flaw in our process, which we are investigating now, Mr Pitner’s credential was not cancelled.”

It was announced yesterday that an Independent Review Panel (IRP) has been established to investigate allegations of corruption in international professional tennis and the effectiveness of existing anti-corruption practices and procedures.

The IRP has been formed as part of the terms of reference and protocols for the Independent Review of Integrity in Tennis, which were announced by international tennis’ four governing bodies - the Association of Tennis Professionals (ATP), the Women’s Tennis Association (WTA), the ITF and the Grand Slam Board.

It follows an investigation by the BBC and Buzzfeed, which claimed that 16 players, ranked in the top 50 in the world across the past decade, have been repeatedly flagged as having potentially thrown matches.

It was also alleged that the players were allowed to continue playing despite reports being made to the TIU, a joint initiative of the ATP, WTA, ITF and the Grand Slam Board.

The IRP will look to review the effectiveness and appropriateness of the TIU, as well as the Tennis Anti-Corruption Programme (TACP) and the Tennis Integrity Protection Programme (TIPP).