Once a month, Mr Mandelson appears before the House for five minutes and answers just one question about the Millennium Dome. Now he could face a whole raft of questions from MPs about why he is not more accountable to them, as the ministerial code on open government requires.
Rhodri Morgan, a Welsh Labour MP and chairman of the Public Administration Committee - one of the most influential in the Commons - has asked officials to look at how previous ministers without portfolio were made accountable.
He will write to Mr Mandelson asking him to explain why he failed to give full answers to written questions from Norman Baker, the Liberal Democrat MP for Lewes. If he is not satisfied with the reply he could decide to hold a full inquiry and call the minister to give oral evidence.
"If the problem persists in the new year there will be a polite note to the minister without portfolio to ask how he can reconcile his answers with the code,'' Mr Morgan told The Independent.
He added that David Clark, who heads the Cabinet Office, Mr Mandelson's department, "has taken a very strong line that, with freedom of information coming in, it is best for ministers and civil servants to get used to it and to get into that spirit now".
Although the committee had no powers to force a minister to answer questions, he added, it did have the power to ask him to explain evasive behaviour.
Mr Baker has written to Mr Morgan to complain that Mr Mandelson never answers oral questions on anything but the dome, even though he sits on 11 cabinet committees and co- ordinates government policy across all departments.
Tony Blair has told Mr Baker in a written reply that Mr Mandelson can be questioned on these wide-ranging issues through written questions. However, the Liberal Democrat MP says Mr Mandelson's written answers have been so evasive that they have broken a ministerial code on open government.
The Code of Practice on Access to Government Information says that ministers "should be as open as possible with Parliament and the public, refusing to provide information only when disclosure would not be in the public interest". It adds that where information is withheld, a relevant exemption under the code - for example national security or commercial confidentiality - must be quoted.
But Mr Baker has compiled a dossier of written answers given by Mr Mandelson which he says do not fit in with the code.
For example, when asked what were the objectives of his recent visit to France, Mr Mandelson replied: "I do not propose to disclose the details of conversations, meetings or other engagements undertaken in pursuance of my duties as Minister without Portfolio."
Mr Baker, who has been a dogged pursuer of Mr Mandelson, asked in November for a list of occasions on which he had complained to the media since 2 May about reporting of the Government, and was referred to an answer given five months earlier to the Conservative MP Nick Hawkins. The answer, when tracked down in Hansard, turned out to be: "No".
When asked to list details of the journeys he had taken at the public expense since May - a question answered in great detail by many other ministers - Mr Mandelson replied: "I have travelled at public expense wherever this has been necessary to the fulfilment of my ministerial responsibilities."
Mr Baker argued that the minister without portfolio was exploiting a lack of clear rules about the duties and responsibilities of someone in his position. He asked the committee to hold an inquiry and to take oral evidence if necessary.
Mr Mandelson's spokesman, Benjamin Wegg-Prosser, said he had asked the Leader of the House, Ann Taylor, for an extra 10 or 15 minutes each month to answer oral questions on the dome. Details of his trip to France had been given just before Christmas - five months after Mr Baker's original query - in response to a question from a newly elected Labour MP, Jacqui Smith.
Some questions, such as those on how often Mr Mandelson spoke to journalists, were too costly to answer.
"The whole point about being a minister without portfolio is that you don't have a portfolio. When Mr Mandelson was given responsibility for the dome he was granted oral time in the House to answer questions like that," he said.
Mr Mandelson asked for extra time at Questions just days before another Commons committee, the Culture, Media and Sport Committee, said his five- minute slot was inadequate. Its report said such was the lack of information on the dome that it was "not so much a journey through time as.... a journey into the unknown".Reuse content