The row over the conduct of the home secretary has continued with news that he could be facing a second investigation.

A review into claims David Blunkett abused his position to speed up a visa application for his former lover's nanny are being urgently investigated by Sir Alan Budd.

And it was reported on Tuesday that parliamentary standards commissioner Sir Philip Mawer had received a separate complaint from a member of the public about the home secretary's decision to allow Kimberley Quinn to travel on a train at the taxpayers' expense.

The journey was paid for using cash intended for an MPs' spouse or partner - Blunkett has said he will repay the costs if found to have breached parliamentary rules.

Sir Philip said that he would now request more information on the complaint before deciding on whether to launch a full investigation.

Amid speculation about Blunkett's future, the Tories have called on the government to widen the remit of the Home Office inquiry.

Shadow home secretary David Davis urged the government to appoint a judge to lead the review.

"The terms of the inquiry are narrowly defined and will answer just one question, not the many," said Davis.

"All of this could have been resolved quickly but there will now be many unanswered questions hanging over the home secretary's head."

The debate was heightened by from Sir Alistair Graham, chairman of the Committee on Standards in Public Life, who intervened on Monday.

He expressed disappointment the government had not accepted recommendations to put in place mechanisms for the "speedy and independent investigation of allegations against ministers".