Michael Portillo last night won a chaotic first ballot of Tory MPs for the party leadership - but a re-run was immediately ordered after two candidates tied for last place.

Former party chairman Michael Ancram and "dark horse" David Davis finished bottom of the poll with 21 votes each.

That meant the candidate who finished last of the five in the contest could not be automatically eliminated.

The announcement of the result was delayed as chairman of the 1922 Committee of Conservative backbenchers Sir Michael Spicer hastily consulted the complex rules of the contest.

Just after 5.30pm, he announced the result and at the same time that a re-ballot of the 166 MPs would take place tomorrow. If there is still a tie for fifth place, both candidates will be eliminated.

The full result, with all Conservative MPs taking part, was: Michael Portillo 49; Iain Duncan Smith 39; Kenneth Clarke 36; Michael Ancram and David Davis 21.

Mr Portillo's supporters claimed their candidate's result was at the "top end" of their expectations and there were calls for both the bottom candidates to step down and allow a clean fight.

But both Mr Davis and Mr Ancram announced, within an hour of the result, that they would not be standing down and would fight in tomorrow's ballot.

Despite the two candidates' protestations, frantic arm-twisting of their supporters will continue until the next vote tomorrow.

After that contest, there is scheduled to be another ballot of MPs next Tuesday which is due to whittle the candidates down to the two whose names would go forward to a ballot of all 300,000 Tory party members, with the winner announced on September 12.