Sir Alan Sugar, Gordon Brown�s enterprise tsar, is facing a challenge to his appointment as a peer that would allow him to join the cabinet.

Sir Alan Sugar, Gordon Brown's enterprise tsar, is facing a challenge to his appointment as a peer that would allow him to join the cabinet.

Sir Alan, star of the BBC television series The Apprentice, was awarded a peerage when he became an enterprise tsar in the government reshuffle last month.

But in another blow to the Prime Minister's authority, a member of the House of Lords Appointments Commission has said that Sir Alan's peerage should be delayed until a sex discrimination case against the entrepreneur is resolved.

An anonymous member of the committee, which has the power to advise but not veto an appointment to the Lords, told Channel 4 News that there were concerns over Sir Alan's immediate appointment.

"There have been cases in the past where we have actually delayed the appointment until we are satisfied. This present situation falls into the same category," said the peer. "There's an allegation of sex discrimination. We don't know what the final outcome is. It's perfectly possible to be able to say just hang on a minute there are issues pending ... because once you have made an appointment it's very difficult to rescind it."

Separately, Lord Oakeshott, a LibDem member of the appointments commission, has called for Sir Alan's peerage to be put on hold. The LibDem Treasury Spokesman, has also attacked the decision to elevate the former Speaker, Michael Martin, to the House of Lords.

The committee vets appointments to the Lords and advises the Prime Minister if it has any concerns about the "propriety" of a nominee. Sir Alan has already had to face down criticism from the Conservatives that his twin roles as government adviser and BBC presenter are incompatible. However, the Appointments Commission is most concerned about the allegations of sex discrimination and bullying, from Hanna Sebright, who was a top executive at a company taken over by Sir Alan last year.

Ms Sebright's employment tribunal will not be heard until the autumn. In a statement, Sir Alan's spokesman said that the businessman would "vigorously defend" himself at the tribunal.

He added: "Sir Alan is surprised that it was thought appropriate to join him personally to these proceedings in circumstances where he has only met the individual concerned on one occasion for no more than 10 minutes."