Senior politicians have admitted that the Brent East by-election result is too close to call.

Ahead of polling on Thursday, early indications are that it will be a race between Labour and the Liberal Democrats.

The main parties are pulling in extra activists and MPs in a bid to boost voting numbers.

Turnout, which will be a crucial factor, is expected to be even lower than in the general election at around 30 per cent.

That could lead to a final vote of just 18,000.

Labour has admitted that motivating its core supporters is proving difficult, largely because of local issues.

It has again received surprise support from the seat's former MP, London mayor Ken Livingstone.

Livingstone, who was expelled from the party, is in the constituency this afternoon to campaign for Labour's candidate, the MEP Robert Evans.

His arrival follows home secretary David Blunkett's rare admission during a visit to the constituency that Labour is "neck and neck" with the Liberal Democrats.

Blunkett conceded that voters in the north London seat are preparing to give a "bloody nose" to the government.

He blamed the Conservatives as part of the reason for the two-way race and slammed Tory party chairman Theresa May's comments that Brent was not "Conservative territory".

"They're saying to people, 'we're not up for it,'" said Blunkett. "It's an absolute disgrace that the so-called major opposition have thrown in the towel. If it had been a three-way race, then there wouldn't have been a problem."

His attacks were rejected by the Conservatives believed the claims were scare tactics aimed at motivating apathetic supporters to boost turnout.

"Nothing has changed; we're fighting to win it. Labour's vote hasn't got any stronger and the Liberal Democrats haven't got the substantial hold as they'd like people to believe," said a spokesman.

Blunkett's comments were seized on by a jubilant Liberal Democrat leader Charles Kennedy who predicted a "photo finish".

Kennedy is making his seventh visit to the constituency and for added measure is bringing 40 of the party's MPs with him.

"We don't usually agree with the home secretary but we do agree with his remarks that it's a close run thing between us and the Labour Party. We can win; it's within our grasp," he said.

The party needs a 27 per cent swing to take the seat but it believes switching from both Labour and the Conservatives, together with the low turnout, will push the Conservatives into third place at the very least.

"It is quite incredible that a party painting itself as a clear cut and coherent opposition is likely to be a lamentable third," he claimed.