International Cricket Council chief executive David Richardson has announced an investigation into how Brendon McCullum's confidential testimony to anti-corruption officials came into the public domain.

New Zealand captain McCullum provided the ICC with testimony of an historic attempt by an unnamed, high-profile player to lure him in with a £100,000-plus offer, reportedly during the 2008 Indian Premier League and on his country's tour of England the same year.

New Zealand Cricket reacted with "dismay" that McCullum's evidence to anti-corruption investigators had reached the public domain and made it clear he was in no way under suspicion of any wrong-doing.

That stance was echoed by Richardson, who said in a statement released by t he ICC: "We recognise that this is a deeply concerning development for the stakeholders in the fight against corruption and we wish to emphasise that Brendon McCullum is not under investigation in this matter.

"Whilst we have privately offered our full support to Brendon, we do so now publicly not only to confirm that, by assisting with the ACSU's enquiries, he has acted quite properly in accordance with his responsibilities as a professional cricketer, but also correct any misperception that he is somehow under suspicion.

"Obviously the ICC considers any leak of any kind of information to be an extremely serious matter, particularly when the nature of the information that has found its way to the media is highly confidential and has been provided in tightly controlled circumstances by individuals to the ACSU (anti-corruption and security unit).

"We are taking all steps available to us to urgently investigate how certain information in the form of statements has come to find its way into the media, so that we can provide reassurances to the stakeholders within the sport so that they can continue to place their trust in the hands of the ACSU and the anti-corruption units of the respective member boards.

"Nobody that did not 'need to know' that information was provided with any of it, so it is with grave disappointment that we find ourselves in this situation today. An investigation is under way that we hope will provide an explanation for how certain confidential information has arrived in the hands of the journalists."

McCullum's leaked statement followed last week's revelations that former Kiwi batsman Lou Vincent was being investigated by the ICC.

Speculation has surrounded the identity of the player accused by the pair, referred to as 'Player X'.

Former Black Caps all-rounder Chris Cairns has strongly denied he is the player in question.

In a statement released to Fairfax Media, Cairns said: "It is well known that the ICC/ACSU has been investigating allegations of corruption and my name has been linked by others to these allegations. I am being asked whether I am 'Player X'.

"Based on the limited information I have received during this investigation, I believe it is being alleged that I am that player. These allegations against me are a complete lie.

"I have never approached Brendon, or anyone else, about match-fixing or any other improper activity."

Richardson would not disclose whether Vincent or any other player has been charged in relation to the investigation.

"On 4 December 2013, the ACSU announced it was carrying out an investigation into the activities of former New Zealand players in historic matches," he said.

"That investigation continues and, as is the position in respect of all other investigations, the ICC does not provide any public comment on the status or outcome at this time.

"Other than to confirm, as is already public, that Lou Vincent has cooperated fully with the ACSU's investigators, it would not be appropriate for the ICC to comment on his position at this stage. Nor is the ICC in a position to identify any other individuals that may or may not have been interviewed as part of this, or any other investigation.

"For confidentiality reasons, and in order not to jeopardise ongoing or future investigations, the ICC is not in a position to provide any information about whether players have been charged or not, or the status of any investigation."