The statement issued by solicitors representing the man, who has not revealed his identity, follows the claims made by former royal valet George Smith.

The aide said Mr Smith was unreliable and accused him of changing his story.

Mr Smith, from Newport, south Wales, waived his right to anonymity by speaking to the Mail on Sunday newspaper about the alleged assault.

The 42-year-old Falklands veteran has also accused the Royal Family of a cover-up.

Tape recording

Details of the alleged rape of Mr Smith emerged following the collapse of the theft case against Paul Burrell, former butler to Diana, Princess of Wales.

During his trial it emerged the princess had kept a cassette tape containing details of a case of alleged male rape of one of Prince Charles' members of staff.

Mr Smith has waived his right to anonymity

The tape, which supposedly consisted of an interview Diana conducted with the alleged rape victim, went missing from a locked chest in Kensington Palace and has never been found, the Old Bailey jury heard.

In the Mail on Sunday, Mr Smith said that in 1996 he told the princess about the alleged rape against him and she recorded his accusation on tape.

In an ITV programme broadcast on Sunday, Mr Burrell told interviewer Sir Trevor McDonald he had no idea what had happened to the contents of the chest.

"They are out there somewhere," he said.

St James' Palace issued a statement on Friday saying there had been a full investigation between October 2001 and February 2002, of events "alleged to have taken place" in the late 1980s.

"When these allegations first emerged in 1996 they were investigated by the Palace and no evidence was forthcoming in support of them and the person concerned did not want to pursue the matter any further," said the statement.

No charges

The allegations re-surfaced and a member of the Royal household was interviewed by police voluntarily in November 2001, the statement said.

But after a review by the police and the Crown Prosecution Service and the Director of Public Prosecutions, no proceedings were brought.

The statement by the man Mr Smith says raped him was issued by Kingsley Napley solicitors.

It said the allegations made to the Mail on Sunday differed "substantially and significantly" from those made to the police last year.

It added that that "must cast serious doubt on Mr Smith's reliability and the accuracy of any allegations he might be persuaded to make".

The statement continued: "Our client has consistently denied that these offences ever took place, and whilst he has no desire to enter into the current media frenzy, cannot allow wholly untrue allegations against him to be reported and unchallenged."

New allegation

It outlines what it says are a number of "demonstrable discrepancies" between what Mr Smith told police in 2001 and his account to the Mail on Sunday.

A spokeswoman for the Prince of Wales said there had been a full police investigation and no evidence had been found.

"If Mr Smith has some new evidence relating to the case, he should provide it immediately," she said.

Mr Smith's interview followed confirmation from Buckingham Palace that a new allegation of male rape, unconnected to his, within the royal household was investigated last year.

A junior member of the Buckingham Palace staff complained of an attack by a fellow worker.

The person concerned did go to the police, but later decided not to proceed with the complaint, the palace said on Saturday.