Two international tennis umpires have been secretly banned, while four others face being thrown out of the sport for life on charges of serious corruption, the Guardian can reveal.

Umpires from Kazakhstan, Turkey and Ukraine are among those alleged to have taken bribes from betting syndicates in exchange for manipulating live scores on the International Tennis Federation’s Futures Tour – which allowed crooked gamblers to place bets already knowing the outcome of the next point.

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The Guardian has also learned that Kirill Parfenov, an umpire from Kazakhstan, was decertified for life in February 2015 for contacting another official on Facebook in an attempt to manipulate the scoring of matches. Yet the tennis authorities never publicly released details, alerting only a small number of tournament directors and national tennis federations.

The International Tennis Federation also kept quiet over the case of another umpire, Denis Pitner of Croatia, who was suspended for 12 months at the start of August 2015 for regularly logging on to a betting account from which bets were placed on tennis matches. The ITF has also never publicly acknowledged that four more officials are facing serious corruption charges, and only did so when prompted by this newspaper.

The Guardian’s investigation will raise fresh concerns about the extent of corruption in tennis and the lack of transparency at the ITF, the governing body of the sport. There are also questions over whether the ITF inadvertently created the conditions for corruption to thrive.

In 2012 it signed a lucrative five-year deal worth $70m with the data company Sportradar to distribute live scores from very small tournaments around the globe. That meant the bookmakers could provide odds on those matches, particularly on the lucrative in-play market, where odds shift as the games progress – and unscrupulous gamblers had a prime opportunity which they could ruthlessly exploit.

Under the terms of the Sportradar deal, umpires are asked to immediately update the scoreboard after each point using their official IBM tablets. This score is then transmitted around the world to live-score sites and bookmakers, allowing the latter to update their prices as the match proceeds.

However, the umpires are alleged to have deliberately delayed updating the scores for up to 60 seconds – allowing gamblers to place bets knowing what was going to happen next. In some cases, the Guardian has learned, umpires are alleged to have texted the gamblers directly before updating the score on their tablet computer.

In effect the umpires are accused of “courtsiding” – a practice among gamblers whereby observing events live can provide an edge before betting markets react to changing scores – and it meant that bets could be placed on the outcome of games and sets in the knowledge that the chances of them winning were much higher than the odds implied.

The ruse was carried out in ITF futures tournaments in eastern Europe, the lowest rung of professional tennis, where there was little or no television coverage or security, and the poorly paid or volunteer umpires were more susceptible to taking bribes.

The Guardian approached Richard Ings, a former professional umpire for seven years who was also a senior executive responsible for umpires at the Association of Tennis Professionals, who said the revelations were “deeply troubling”.

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“Over a 15-year period I have been involved in professional tennis officiating both as a professional umpire and administrator of officiating for the ATP,” he said. “During that period I have seen tennis umpires breach the code for officials for relatively minor offences. But I have never before seen umpires breach it for tennis-integrity issues related to gambling on tennis and courtsiding.

“It is deeply troubling, but not at all surprising, that the risk to the integrity of tennis driven by gambling has expanded beyond players and their entourages to now include umpires and other tournament officials.”

In 2014 the French umpire Morgan Lamri, who worked on the Challenger and Futures tours, was banned for life after being found guilty of being in breach of four unspecified articles of the Tennis Integrity Unit’s rulebook. However this is the first time that so many umpires – those charged with protecting the integrity of the game – have either been banned or faced bans.

Senior figures inside the sport have told the Guardian they fear the allegations are more damaging than the recent more historical claims around match-fixing, for several reasons.

• It shows that corruption extends beyond players’ fixing matches and into those who are supposed to be the game’s arbiters.

• It also exposes the fault lines in tennis’s claims that is doing all it can to be transparent. In the past the names of players who have been banned for life have always been publicly released. Yet here the ITF stayed quiet until it was pressed by the Guardian.

• The revelations raise the question as to whether the ITF decided not to release that fact that Parfenov and Pitner had been suspended because it feared the embarrassment.

• It calls into question whether the ITF’s $14m-per-annum contract with Sportradar has acted as an inadvertent facilitator of corruption. By providing a live data stream from those events most vulnerable to corruption due to small prize pools, a lesser degree of oversight, and negligible media attention, did it help corruption thrive?

In a statement, the ITF said that it could not comment further on the four officials are who currently suspended pending the completion of ongoing investigations.

“In order to ensure no prejudice of any future hearing we cannot publicly disclose the nature or detail of those investigations,” it added. “Should any official be found guilty of an offence, it will be announced publicly. The ITF code of conduct for officials was amended in December 2015 to include public reporting of officiating sanctions from 2016 onwards.

It also insisted that the Sportradar deal had helped the game expose corruption, not fuel it.

It added: “Our deal with Sportradar, like those in place with ATP and WTA, by creating official, accurate and immediate data, acts as a deterrent to efforts by anyone trying to conduct illegal sports betting and/or unauthorised use of data for non-legal purposes.”

The revelations have also renewed the spotlight on a sport stung by claims at the Australian Open that players on the men’s main ATP tour have fixed matches.

Partly due to the explosion in the number of events that can be gambled on during play, the number of suspicious incidents flagged up by bookmakers has risen sharply in the past three years.

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Figures from the European Sports Security Association, a trade body that represents 18 bookmakers including William Hill and Ladbrokes, show that 49 suspicious gambling alerts were raised about tennis in the first nine months of 2015. In contrast, only 16 alerts were raised about other sports over the same period.

The world No2 Andy Murray has already urged the game’s authorities to be more “proactive” – warning them that “as a player, you just want to be made aware of everything that’s going on. I think we deserve to know everything that’s out there”.

Senior sources within the sports integrity community believe that the introduction of the Tennis Integrity Unit (TIU) in 2008 has helped stem the flow of new cases at the very top of the game. But they fear the TIU, which is supposed to be the sport’s watchdog, does not have the resources or power to tackle widespread abuse at the lower rungs of the tennis ladder.

During the Australian Open a combined statement from the ATP, WTA, ITF and heads of all four grand slam events, announced an independent review into the TIU “aimed at further safeguarding the integrity of the game”.

That review, headed by Adam Lewis QC, will also address issues of transparency and resourcing at the TIU and how to extend the scope of tennis’s anti-corruption education programmes.

As the TIU board chairman, Philip Brook, admitted last month: “It is vital we repair the damage and do so quickly. We are determined to do anything we need to remove corruption from our sport.”

How the scam worked

• Tennis umpires at low-level professional events often input scores manually on to an IBM tablet. The scores are thereby transmitted to the ITF’s data partner, Sportradar. Bookmakers access this scoring data from Sportradar to service their in-play, or live betting markets, where bets are placed and often cashed out while the game is in progress.

• The four umpires who have been suspended are alleged to have deliberately delayed the inputting of these scores, thereby giving gamblers, some of whom may have been present at courtside, 30 seconds to a minute of advance warning before the betting odds moved in response to the updated score. In some cases, the umpires were texting the score directly to gamblers before it had been officially updated.

• Gamblers could therefore manipulate and take advantage of minor shifts in the in-play market through knowing the scores in advance of the odds shifting to reflect them.