As ballot papers went out in London for Labour's mayoral selection contest, Prime Minister Tony Blair urged members to vote for Frank Dobson.

Mr Blair told a meeting in Southall, west London, Mr Dobson was a team player. But his speech was markedly less critical of Ken Livingstone.

He told an audience of 500: "It is your decision, you decide but we have been two and a half years in government after 18 years in opposition, don't let us do anything to throw it all away."

Mr Blair has urged Labour's rank and file to support the former health secretary rather than the former leader of the GLC. Mr Livingstone, Mr Dobson and the third candidate, ex-transport minister Glenda Jackson, are making a final push for votes as Labour members receive their voting papers.

Members have until 16 February to cast their votes but most are expected to do so by the end of this week.

'We need a team player'

At Wednesday's question-and-answer session in Southall Mr Blair, asked if he thought Mr Livingstone had changed since the GLC's heyday in the early 1980s, said: "If he has not we have a problem."

The prime minister said: "The London mayor is important. It is important we have a team player and it is important we have someone who can deliver the goods.

"I have worked with Frank Dobson for many, many years. I have worked with him two and a half years in government, he is a man I trust and he is a man you can depend on."

Mr Prescott focused his assault on Mr Livingstone's plans to use bonds to raise money to modernise the Tube, saying they would cost £4.5bn - "That's £4.5bn less to spend on hospitals, schools or tackling crime."

He said of Mr Livingstone's plans for issuing New York-style bonds to finance improvements to the Tube: "If you do bond financing on its own you will have to raise taxes. I prefer the private sector to carry the risk."

Dogged by controversy

The Labour leadership's latest bid to persuade members to support Mr Dobson came the day after party managers bowed to demands for a review of the way future internal elections are held.

The party's mayoral selection contest has been dogged by accusations of dirty tricks and bias on the part of Labour officials. Mr Dobson is facing possible action by the Data Protection Registrar following his use of central membership lists received from the party's Millbank headquarters.

In his latest mailshot to Labour members, sent out this week, the ex-minister said his ambition for the mayorship was to "unite London."

But he renewed his attack on Mr Livingstone: "I have known Ken a long time and he is a very engaging politician."

"However, the truth is that those across the party who know him best don't trust him. Be in no doubt that Ken, who has used this campaign to attack our government, would do so even more vigorously as mayor."

'No negative campaigning' - Livingstone

Each candidate sent out a short election message with the ballots. Mr Dobson's promised full employment and a "relentless drive against poverty".

Ms Jackson said her priority would be tackling homelessness and promised "Midnight Express" Tube and rail services which will run until the early hours of the morning.

Mr Livingstone promised "no negative campaigning by my supporters in this selection" and said he would reach out to Labour's "core support".

Ms Jackson, though expected to come in some way behind her two rivals in the final reckoning, has been polling ahead of Mr Dobson.

But the winner of Labour's nomination is being decided by an electoral college made up of one third London MPs, MEPs and Greater London Assembly (GLA) candidates, one third affiliated trade unions, and a final third of party members.

Most MPs, MEPs and GLA hopefuls are expected to follow their party leader and vote for Mr Dobson. Unions holding internal ballots are expected to back Mr Livingstone; those not balloting, Mr Dobson.

Mr Livingstone is expected to win a majority in the membership section but needs around 65% to be confident of victory through the college.

London's mayoral election takes place on 4 May.