Will housing minister ride in as stalking horse to unseat Brown?

The usually loyal minister was named by several Labour sources as the perfect candidate to flush out other more heavyweight contenders from the Cabinet to topple the Prime Minister.

However, Ms Flint refused to be drawn into the discussion, saying she had a job to do and that the party already had a leader in Mr Brown.

But one senior source told The Scotsman Ms Flint's name was in the frame as opposition to Mr Brown grew from within his own ranks.

The source said: "It needs to be someone below the rank of David Miliband (the Foreign Secretary] and Alan Johnson (the Health Secretary] both of whom won't do it now. Someone like Caroline Flint would be ideal."

Another usually loyal MP said that Ms Flint was one of a number of ministers worried about the party's prospects and that could force her into action.

Under Labour leadership rules, a fifth of Labour MPs – 71 of the current intake – are needed to back a challenge.

Nominations need to be sought prior to the party's autumn conference although there does not appear to be a rule about how far in advance this should be.

A spokesman for Ms Flint last night told The Scotsman: "The Labour Party has a leader. It's Gordon Brown and while he is getting on with his job, Caroline is getting on with hers."

Another government source told The Scotsman that "Ms Flint certainly looks glamorous but I can't see her getting the support of 71 Labour MPs".

While there doesn't seem much belief that the 46-year-old could actually win, a leadership vote could seriously damage Mr Brown's standing and then other Cabinet figures could justify challenging him.

Ms Flint, a mother of two, divorced her first husband and is now married to Labour activist Phil Cole, who has one son.

The party faces a tense conference later this month after other less publicly loyal MPs demanded a challenge to Mr Brown.

The 12 confirmed rebels include: Siobhain McDonagh, who was sacked as a junior whip; Barry Gardiner, who left his post as special adviser on forestry matters; Jim Dowd, Lewisham MP and his partner, Janet Anderson a former culture minister; Joan Ryan, who was vice-chair of the party; Fiona Mactaggart, a former Home Office minister; George Howarth, another former minister regarded by some as a key ring-leader; Gordon Prentice, the maverick left-winger; John McDonnell, leader of the Labour left campaign group; Greg Pope, a former whip; Graham Stringer, an outspoken government critic and Frank Field, the former welfare minister.

So far, there is little evidence the campaign is orchestrated.

But there has been speculation that John Reid, the former Home Secretary and now Celtic chairman, was supportive of any challenge. Mr Reid, a known critic of Mr Brown has kept publicly quiet on the Prime Minister's leadership woes.

One source said: "No doubt John is telling people, 'I told you Gordon would be a disaster', but he is a bit distant from the action now so is not likely to be behind any orchestrated attempts".

Mr Reid, MP for Airdrie and Shotts, did not respond yesterday to The Scotsman's questions about whether he endorsed Mr Brown in continuing in his role.

Yesterday, Ladbrokes cut the odds for him becoming the next Labour leader from 20/1 to 16/1, although he is due to stand down at the next election.