Home Secretary David Blunkett's future is in question after revelations about his private life. Here, at a glance, is a basic guide to the furore.
What is David Blunkett alleged to have done wrong?
The most serious allegation is that he intervened in a visa application for the nanny of his ex-lover Kimberly Quinn. As the Cabinet minister with overall responsibility for immigration, that would be a conflict of interest at least. It would also breach the ministerial code. Letters published in Wednesday's Daily Mail appear to show that the nanny's visa application was dealt with within 19 days, rather than the year it normally would have taken at that time.
Other claims are that he tipped off Mrs Quinn's parents about a security scare at Newark Airport near New York, gave her a first-class train ticket which had been assigned to him, took her to Spain accompanied by bodyguards, ordered his official chauffeur to drive her between London and his Derbyshire home and stationed a police officer outside her home during a demonstration.
What does Mr Blunkett say about the claims?
He says the Newark security scare was already in the public arena, that his bodyguards were in Spain to protect him, and that Mrs Quinn only had lifts in his official car on trips his chauffeur was already scheduled to make on government business.
He initially said he thought he was entitled to claim for the train tickets but now admits he made a "genuine mistake" and is paying back the £180 fare to Parliament.
On the most serious claim, that he intervened in his ex-lover's nanny's visa application, he acknowledges that he checked it was filled in properly but denies intervening to get it approved.
What is the background to the claims?
Mr Blunkett had a three-year affair with Spectator publisher Mrs Quinn, who is married to Vogue publisher Stephen Quinn.
The affair has ended but Mr Blunkett has claimed he is the father of her two-year-old son - and that the child with which she is now pregnant is also his. She has contested this.
What inquiries are happening?
Ex-civil servant Sir Alan Budd has been appointed by the Home Office to look at the claims about the visa application.
Parliament's standards watchdog, Sir Philip Mawer, has received a complaint from a member of the public about the rail tickets and says he will look at the evidence before deciding whether to investigate.
Downing Street says the Home Office will examine the less serious issues.
What do the opposition parties think of the claims?
Shadow home secretary David Davis has called for Sir Alan's inquiry to examine all the claims, not simply the one relating to the visa application.
But he has said if it was simply a case of Mr Blunkett having checked the application was filled in correctly, as he insists, it would have been "unwise" for the home secretary to have become involved, but not "fatal".
The lesser claims, which have been answered by the home secretary, are not seen as particularly damaging.
What is the government's position and will Mr Blunkett keep his job?
The prime minister has offered his full support, saying Mr Blunkett retains his "full confidence".
And Tory leader Michael Howard, while supporting the need for an inquiry, has said he hopes it clears Mr Blunkett.
If the inquiry clears the home secretary of breaking any rules, he will probably continue with his job.
If, on the other hand, it finds he did act improperly he would almost certainly have to resign.
However, the Tories have argued that Mr Blair's claim the inquiry will exonerate Mr Blunkett has prejudiced it.
What happens next?
Sir Alan's inquiry will start to take evidence and is expected to report back quickly.