Labour contender for London mayor Frank Dobson has attacked the use of a controversial electoral college to pick the party's candidate, saying that it had caused him political damage.

He was speaking after the Prime Minister Tony Blair once more threw his weight behind his former Health Secretary, Mr Dobson said the system that gives a third of the vote each to MPs, unions and party members had done him "harm".

The Labour party has sent out ballot papers to its 48,000 members in the capital. Although the papers do not have to be returned until 16 February, the candidates believe many will make up their minds within quickly, making the next few days crucial in deciding who will become the Labour candidate.

The former health secretary told the BBC that the electoral college - which had been seen as giving Mr Dobson a clearer chance of victory than a simple ballot of party members - had been the idea of party workers at Millbank Towers.

"There are quite a few of them who think they are clever and are on the inside track," he said.

"They ring political correspondents or sidle into bar where there are journalists and start tittle-tattling and that's certainly been no good - and it was they who decided on the idea of an electoral college."

Mr Dobson added: "When I decided to stand I believed, like everybody else did, it would be decided by one-member-one-vote and I believed I would win under that system.

"And then the electoral college was introduced and I believe that has done me a great deal of harm because I have been associated with it."

Mr Dobson's facing a neck and neck finish with his main rival Labour left-winger Ken Livingstone, while the third candidate

Glenda Jackson, bringing up the rear, is regarded by many party members as a potential kingmaker who could swing her supporters behind either of the two men.

Blair's warning

On Wednesday Mr Blair told party members to vote for Mr Dobson saying: "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."

Deputy Prime Minister John Prescot also put his weight behind Mr Dobson warning that Ken Livingstone's plans to finance Tube re-development with a bonds issue would leave tax-payers picking up the bill.

When asked if the close backing given to him by the party leadership was damaging Mr Dobson said it was "manifestly barmy" to say he was attempting to distance himself from the prime minister.

He said journalists "used to portray me as the bearded old Labour cuckoo in the new Labour nest - I'm still the same person.

"I am certainly not trying to distance myself from Mr Blair.

"Mr Blair is the most popular prime minister the Labour party has ever produced, he presides over the most successful Labour government there has ever been."