David Cameron shrugged off the row over his candidate’s attendance at a Labour fundraising event as he made his fifth visit to Ealing Southall yesterday before tomorrow’s by-election.

Rivals have inundated voters in Ealing Southall with photographs of a smiling Tony Lit, the Tory candidate, greeting Tony Blair last month at an event for which his company paid Labour £4,800.

The Tory leader will be closely associated with the result in Ealing Southall, where his campaign was billed as an example of his brand of modern Conservatism in action and his candidate will be described on the ballot paper as “Tony Lit – David Cameron’s Conservatives.”

The Tories sought to throw the spotlight back on Labour by publishing a letter from their campaign co-ordinator, the Tory MP to Grant Schapps, to the local police commander asking that extra officers be stationed outside Southall polling stations “to provide reassurance to voters and to prevent any fraud or intimidation”.

It follows allegations of a scuffle at a Hindu temple in Southall where Mr Lit was trying to address worshippers on Sunday evening and, the Tories say, followed objections from some Labour supporters present. The Conservatives also insisted there had been no breach of electoral law when doctors and nurses who support the party gave free health checks to voters in Southall last weekend.

A Tory spokesman said that the party sought advice beforehand and was confident that in offering checks of blood pressure and body mass index and giving dietary advice they were not in breach of the law banning inducements in elections, since some clinics and pharmacies offered these tests free.

The Liberal Democrats seized on a blunder by the Labour campaign to accuse the party of complacency after it send out a residents’ survey with a printed return address styling their candidate “Virendra Sharma MP”.

Chris Rennard, the Lib Dem chief executive, said: “Labour’s assumption is incredibly arrogant. It is yet another example of the way that Labour have taken this area for granted over the years. Instead of assuming people will vote for him, Mr Sharma should be dealing with the problems of local people.”

Hilary Benn, the Environment Secretary, made a campaign visit for Labour yesterday to chat to parents at the gates of a school in the area where he was an Ealing councillor for 20 years.

Today the Lib Dems have campaign walkabouts in the constituency from both Sir Menzies Campbell, making his fourth visit in as many days, and Charles Kennedy, whom he replaced as leader and whose friends blame Sir Menzies for his downfall. The pair will make separate visits, Mr Kennedy at lunchtime and Sir Menzies later in the afternoon, but Lib Dems said this reflected “diary constraints” and not animosity between the two.

Bookmakers have made the Lib Dems second favourites in the seat, pushing the Conservatives into third place, since the revelations at the weekend of Mr Lit’s attendance at the Labour fundraising event.

But two figures associated with Mr Kennedy’s leadership put pressure on Sir Menzies, saying that unless the party achieved a strong result in Ealing Southall, his position could be under threat.

Lord Razzall, who chaired the past two Lib Dem general election campaigns for Mr Kennedy, told BBC Radio 4’s World at One: “There are clearly some people in the party who are complaining about Ming as leader and I think a lot of them are using the Ealing by-election as a sort of catalyst to bring things to a head. My own view is that would be a serious mistake. We would look silly if we were to attempt to change the leader and a lot of the criticisms of Ming are unfair.”

Mark Littlewood, the party’s former head of communications, said: “The truth of the matter is that over the last year or so, the Liberal Democrats’ electoral performance has been somewhat underwhelming.

“Ealing Southall is by no means home turf for the Liberal Democrats, but if you wanted the sort of electoral test in which you would expect the party to do well, surely this is it.” He added: “The truth is, if you believe the opinion polls, the party has lost perhaps 4 per cent or 5 per cent of the vote since the last election. If that dropped much further or if Liberal MPs with majorities of one or two thousand started to think that their future prospects could be in danger, then I think that you would see change.”

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