Jeremy Middleton is a company director

Conservative chiefs will hope that Jeremy Middleton's selection will quiet criticism of the time it has taken to choose a candidate.

Party workers feared their rivals had been given a head start in the contest.

Tory co-chairman Dr Liam Fox said it had been "worth waiting to find such an excellent local candidate".

He added: "We were determined to get the best, and we did.

'Crucial test'

"He will fight a first-class campaign to expose the failings of the government in a by-election which will be a crucial test both of Tony Blair's credibility as leader of the Labour Party and of whether any Labour seat can now be considered safe."

Lib Dem campaign chief Lord Rennard claimed his party was in a straight fight with Labour for the seat and the "sacrificial lamb" chosen by the Tories would be reduced to a scrap for third place with the UK Independence Party.

But the Tories insisted they would fight a "very robust" campaign.

"We've been waiting to get the best local candidate and that's what we've done," an aide to Tory leader Michael Howard told The Financial Times.

The contest is expected next month.

Local candidates

Mr Middleton, 43, who is married with three children, is a director of HomeServe plc, a Newcastle-based industrial services company he co-founded in 1992.

The company operates nationally with a turnover of over �250m and it employs more than 2,000 people.

Other Hartlepool candidates are: Labour's Iain Wright, 32; barrister Jody Dunn, standing for the Liberal Democrats; Stephen Allison, 44, standing for the UK Independence Party and John Bloom, standing for Respect.

Labour is defending a 15,000 majority in the seat made vacant by the appointment of Peter Mandelson as Britain's European Commissioner.

All of the parties have opted to field local candidates, after high profile figures such as Middlesborough mayor Ray Mallon, courted by both the Tories and Labour, and UKIP MEP Robert Kilroy-Silk ruled themselves out of the contest.