Kazakhstan's Kirill Parfenov was banned for life in February 2015 while Croatia's Denis Pitner received a 12-month sanction in August of the same year, but details of the punishments only emerged yesterday.

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

The organisation, however, claims a rule allowing it to make the names public was only changed in December.

It is alleged that bribes were taken by the umpires to manipulate matches on the ITF's Futures Tour, a low-level competition.

This allowed gamblers to place wagers already knowing the outcome of points, it is claimed. 

According to the Guardian, the four umpires who remain under scrutiny are thought to have delayed the input of scores by up to a minute, which allowed syndicates to place their bets.

Parfenov received his ban for speaking to another official on Facebook in a bid to manipulate the scoring of matches, while Pitner was found to have sent details about a player's well-being to a coach during a tournament.

The Croatian also logged on to a betting account from which bets were placed on tennis matches, with both of the banned umpires facing their punishment after an investigation by the Tennis Integrity Unit (TIU).

The ITF is based in London and has now been summoned to appear at a hearing of the Culture, Media and Sport Select Committee in the Spring, The Guardian says.

Conservative Member of Parliament Damian Collins, who sits on the committee, said: "The Tennis Integrity Unit is only really accountable to other people in tennis.

"There’s no outside scrutiny.

"It needs more resource and proper independent scrutiny.

“They seem to have been in denial about the scale of the problem.

"Everyone in tennis knows it’s a huge problem.

"The TIU seems to be a Wizard of Oz type operation - they speak with great authority but behind the curtain there’s only one man.”

Collins also said that the ITF should consider not allowing betting on low level tournaments.

He sat on the Committee when it questioned Britain's International Association of Athletics Federations (IAAF) President Sebastian Coe on blood doping in December, with British authorities perhaps having more authority over the ITF due to it being based in the country. 

It is not known who from the organisation would appear, with American President David Haggerty being elected into his role in September, replacing outgoing Italian Francesco Ricci Bitti. 

The situation follows allegations of match-fixing in tennis being revealed on the eve of the Australian Open last month.

An investigation by the BBC and Buzzfeed 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, which is a joint initiative of the Grand Slam Board, the ITF, the ATP World Tour and the Women's Tennis Association (WTA).