PR guru Max Clifford has denied claims by former royal butler Paul Burrell that he breached his confidentiality by passing personal details about him to the News of the World.
The claims by Mr Burrell - once known as Diana's "rock" - are an "affront to common sense", Mr Clifford said in a statement issued by his solicitor Dan Morrison.
"The claims made by Mr Burrell have no merit. His allegations are opportunistic and are denied," the statement said.
"It is an affront to common sense to suggest that Mr Burrell, who has sold stories to the newspapers, made countless appearances on TV and has even written a book about his dealings with the Royal Family, now feels able to claim that any information he provided was confidential.
"We will defend these claims in court and will be asking the judge at the earliest opportunity to strike out these claims as having no prospect of success and an abuse of process."
The denial comes after Mr Burrell's lawyer Mark Lewis confirmed papers have been lodged at the High Court alleging breach of confidentiality by Mr Clifford.
Mr Burrell has claimed he hired Mr Clifford to limit bad press coverage about him a decade ago, but rather than stopping stories, the publicist passed them to the now-defunct News of the World, Sky News reported.
The claim emerged after Mr Clifford said he would try to continue to lead a normal life after being arrested by detectives investigating the Jimmy Savile sex abuse scandal, describing the allegations against him as "totally untrue".
The publicist was questioned last week on suspicion of sexual offences as part of Operation Yewtree, the investigation into allegations of sex abuse surrounding Savile and others.