Two government departments have come under fire for their failure to disclose information relating to the Hinduja passports affair.

The Home Office and the Cabinet Office have been accused by the parliamentary ombudsman, Sir Michael Buckley, of withholding vital papers relating to the events that eventually forced the resignation of Peter Mandelson.

Investigating a complaint from a journalist, Sir Michael rejected former home secretary Jack Straw's argument that the documents could not be published because they would have prejudiced the inquiry being conducted by Sir Anthony Hammond.

The unnamed journalist said the Home Office had failed to provide him with the information contained in an alleged telephone conversation between the Peter Mandelson and Mike O'Brien.

He had also complained that the Home Office had refused to provide him with the dates of all letters relating to the Hinduja brothers written by Keith Vaz to the Home Office since May 1997, and the information contained in them.

The watchdog criticised the Home Office for failing to maintain its files on the highly sensitive issue "in anything approaching an adequate manner".The Cabinet Office, which had become involved as the custodian of papers from Mandelson's private office, also came under fire.

At one point officials "appeared to be withholding papers, which they readily acknowledged existed, from my investigation".

"I was deeply concerned at this development. Such a refusal strikes at the very heart of my office's function and effectively made my investigation unsustainable," said Sir Michael.

Both government departments subsequently apologised for their behaviour and made the papers available.

The ombudsman partly upheld the complaint, and criticised both the Cabinet Office and the Home Office for their lack of co-operation.

He accepted that there was no direct record of a telephone conversation between the two Ministers and that, therefore, there was no information to be disclosed under the Code.

Shadow Cabinet Office minister, Tim Collins, called for the government to apologise.

"It is now imperative that the deputy prime minister make a formal apology to the House of Commons for the misconduct in the Cabinet Office foundby the parliamentary ombudsman," he said.

"It is increasingly clear that this government will break any parliamentary rule in the book to cover up its activities in the growing list of 'cash for favours' scandals."

Liberal Democrat home affairs spokesman, Norman Baker, said the criticisms of the departments were a serious matter and called on the government to explain its actions.

"It is a very serious matter that the Cabinet Office was withholding documents from the Ombudsman. This is a challenge to the very heart of the democratic process," said Baker.

"It also shows that the government, while maintaining on the surface that there was nothing to hide, was paddling furiously under the water to keep information from the ombudsman," he said.

A Home Office spokesman accepted there were "lessons to be learned" and the Cabinet Office said it had apologised for its failings.