Allies convinced Clarke will not stand despite his long-held leadership ambitions

Kenneth Clarke was under growing pressure last night to join the Tory leadership battle to keep the flag flying for the party's centre left.

Many of the former chanc- ellor's natural allies were dismayed that the contest appeared to have already been carved up by the Right.

Although he has privately admitted to still harbouring leadership ambitions, his allies insisted last night he was not about to change his mind and stand. One said: "He's been through that twice and lost. He wouldn't want to do it again."

His admirers argue he is the Tories' best hope to make the party electable again. He is feared by Labour and the Liberal Democrats, and has the charisma to reach out to floating voters and win back the centre ground.

A series of other potential standard bearers for a centre-left modernising agenda look certain not to put their names forward. Michael Portillo, 50, once viewed as heir apparent to the Tory party, has abandoned his leadership ambitions in favour of a media career.

Since his ill-fated leadership bid two years ago, Mr Portillo has emerged as a sought-after political pundit. This month, he successfully took on the role of a "single mother" looking after four children on a tight budget in a run-down area.

Fellow moderniser Tim Yeo is expected to rule himself out of the contest today. After the Tories' shattering election defeat in 1997, he became an enthusiastic convert to the modernising agenda, calling for the party to debate drug laws and adopt a more relaxed attitude to single-parent families. Mr Yeo, now 58, served under Iain Duncan Smith in two capacities, shadowing the Culture, Media and Sport and Trade and Industry departments. But his relationship with his leader was always arm's length and recently he candidly admitted the party still had a "mountain to climb" to win power.

Theresa May, the party chairman, had also been viewed as a modernising force committed to bringing more women and ethnic minorities into active Tory politics. She controversially told activists at their 2002 conference that they were perceived as the "nasty party". But her instinctive loyalty is likely to dissuade her from fuelling further division by standing. Although she has held high-profile positions in recent years, she has no real powerbase within the heart of the parliamentary party.