World tennis was rocked on Monday 18 January by allegations that the game's authorities have failed to deal with widespread match-fixing, just as the Australian Open, the first grand slam tournament of the year, kicked off in Melbourne.

Tennis authorities rejected reports by the BBC and online BuzzFeed News, which said 16 players who have been ranked in the top 50 had been repeatedly flagged to the Tennis Integrity Unit (TIU) over suspicions they had thrown matches in the past decade. Eight of those players were taking part in this year's Australian Open, the BBC and BuzzFeed News said.

However Chris Kermode, chair of the sport's governing body the Association of Tennis Professionals (ATP), said: "The Tennis Integrity Unit and the tennis authorities absolutely reject any suggestion that evidence of match fixing has been suppressed for any reason or isn't being thoroughly investigated."

"While the BBC and BuzzFeed reports mainly refer to events from about 10 years ago, we will investigate any new information," Kermode told a hastily-arranged media conference at Melbourne Park.

The media reports, which follow corruption scandals in world football and athletics, created a stir at the event at Melbourne Park, with players expressing surprise at the allegations. "When I'm playing, I can only answer for me, I play very hard, and every player I play seems to play hard," women's world number one Serena Williams told reporters. "If that's going on, I don't know about it."

The BBC and BuzzFeed News said the TIU, set up to police illegal activities in tennis, either failed to act upon information that identified suspicious behaviour amongst players, or impose any sanctions. All of the 16 players, including winners of grand slam titles, were allowed to continue competing, the media reports added.

TIU director of integrity Nigel Willerton told reporters in Melbourne he would not comment on whether any players on the pro tour were under investigation, saying it would be inappropriate to do so. The BBC and BuzzFeed News said they had not named any players because without access to their phone, bank and computer records it was not possible to determine whether they took part in match-fixing.

The media reports said the 2007 ATP inquiry found betting syndicates in Russia, northern Italy and Sicily making hundreds of thousands of pounds betting on games which investigators thought to be fixed. Three of these games were at Wimbledon. In a confidential report for tennis authorities in 2008, the inquiry team said 28 players involved in those games should be investigated but the findings were never followed up, the news organisations said. Tennis authorities introduced a new anti-corruption code in 2009 but after taking legal advice were told previous corruption offences could not be pursued, they added. Kermode added he was disappointed the story had taken attention away from the tournament.

"We are confident that the Tennis Integrity Unit is doing what it can and tackles this issue very, very seriously," Kermode said.

TIU investigations had resulted in sanctions against 18 players, with six issued life bans, he added. Kermode also rejected suggestions the TIU was under-resourced and did not have necessary enforcement powers. Tennis authorities have pumped about $14m (£9.8m) into anti-corruption programmes, Kermode added.