Two Conservative MPs are considering jumping ship to Nigel Farage’s party if it wins the Rochester and Strood byelection, Ukip candidate Mark Reckless said on Wednesday.

Reckless, the former Tory MP whose defection triggered the contest, made the claim on the eve of a vote likely to return him as Ukip’s second MP. Further defections would be likely to prompt a crisis in Downing Street about the haemorrhaging of the Tory vote six months before the general election, and potentially a move on David Cameron’s leadership.

Reckless, the clear favourite to win, said: “During the campaign I have spoken with two Conservative MPs about the possibility of their moving over and I think they will want to see what the result is before making any decisions. One of them I had discussions with by telephone and the other I met in an undisclosed location, not in the constituency. It is a very individual decision. And I feed back to Nigel [Farage] on those conversations.”

Eric Pickles, the Conservative communities secretary, said on Wednesday he was certain his party could win in defiance of the polls, and dismissed the idea of more defections.

Campaigning outside Rochester town centre, he said: “I don’t think there will be any [defections]. We have brought the economy back from the brink … at times when we talk to our friends in Ukip it sounds as though the only thing they really like about our country is its past.”

Reckless’s comments are likely to provoke strong speculation about possible candidates for joining Ukip.

One of the favourites is Peter Bone, the Eurosceptic Conservative MP for Wellingborough, who is speaking in a debate on Thursday in Cambridge in favour of the motion that Ukip has been good for British politics.

Asked whether he was about to defect, Bone did not specifically deny it, although he called for Ukip members to reunite with the Conservatives on the centre-right. “You’ve seen what the motion says,” he said. “It’s quite clear. It says Ukip is a good thing for British politics which in my view it is to have another party which is pushing the Europe debate on and about immigration. It’s helped moved it along.

Nigel Farage, left, and Peter Bone in the studios of ITV’s Daybreak programme last year. Photograph: Steve Meddle /Rex Features

“My view is that Ukip membership should come back and join the Conservatives and be part of a centre-right majority in this country.”

Other possibles are John Baron, the MP for Basildon and Billericay, who has said “never say never” to the prospect of defection.

He was treated with kid gloves in the House of Commons by the prime minister on Wednesday as he asked an awkward question about what the government is doing about nuclear test veterans.

Conservative paranoia about defections was also fuelled when a picture emerged of Mark Pritchard, the party’s MP for The Wrekin, photographed smiling next to Farage at an event.

The Tory rejected the idea he was about to join Ukip, telling the International Business Times that it was just a “friendly photo, not a sign of any political allegiance”.

Attention has turned to the possibility of defections as Reckless looks set to triumph in the north Kent constituency, despite Cameron’s promise to throw the kitchen sink at the seat.

If returned, he will be Farage’s second MP, after Douglas Carswell defected from the Conservatives and then won back the seat for Ukip in the Essex seaside town of Clacton.

As the campaign entered its final day, it descended into acrimony over the issue of immigration, with Ukip’s candidate accused by Labour of endorsing the idea of repatriation for some EU immigrants.

Speaking in an ITV hustings, Reckless suggested that some European migrants, such as a Polish plumber, should only be allowed to stay for a fixed period on a work visa if the UK left the EU as advocated by his party.

Yvette Cooper, the shadow home secretary said: “To hear the language of repatriation coming from someone they [Ukip] hope will be their second MP is shameful.

“It’s a policy that comes straight out of the last BNP manifesto and does not reflect British values.”

Ukip was forced to clarify that it is in favour of allowing all existing EU migrants to stay, suggesting Reckless had misunderstood the question. The Ukip candidate then went on to infuriate the Conservatives by accusing them of being the ones who were conducting a “BNP-light” style campaign.

The Tories have been campaigning particularly hard on the issue of immigration, with their candidate Kelly Tolhurst saying she wanted Cameron to take more action.

In a sign of the party’s fears about seeming soft on immigration, she refused to condemn the idea of EU migrants being asked to leave the country, simply criticising Reckless for changing his mind about his views.

She also distributed a letter, which does not mention the Conservatives, that juxtaposed a statement about reducing immigration and a line about people not feeling safe on the streets.

Tolhurst said she was still hopeful of winning, but she was reduced to begging for votes from supporters of other parties in a bid to keep Ukip out of the constituency.

“It’s a two-horse race and the reality of it is if we don’t want to wake up to a Ukip MP on Friday 21st November then people who would normally be voting for Labour, the Lib Dems and or anyone else, then they need to be voting for me,” she said.

In contrast, Ukip was in victory mode, with dozens of its staff, politicians and activists gathering for a lap of the town in a party-branded bus.

Possible defectors

Philip Hollobone. Photograph: Stuart Clarke/Rex

Philip Hollobone, the Eurosceptic MP for Kettering, is seen as one of the most likely defectors. He is a regular rebel who is one of four Tory MPs who are carrying out local polls on Britain’s EU membership in the same way as Reckless and Carswell did before their defections.

Hollobone, who has denied he is planning to defect to Ukip, is also a supporter of the anti-EU Better Off Out group. In a statement on its website he said: “Millions of British people have never had the chance to vote on whether or not to be in the EU. In 2006, you have to be at least 49 years of age to have taken part in the last UK referendum on Europe.”

Philip Davies. Photograph: Rex

Philip Davies, MP for Shipley who, is a member of the Better Off Out group, regularly confronts Cameron over Europe. But their humorous exchanges – and his friendship with the work and pensions minister Esther McVey – suggest Davies would be expected to think very carefully before defecting

In his statement on the Better Off Out group website, Davies wrote: “Our country built our prosperity as world traders. Our future prosperity depends on us trading with China, India, the rest of the Commonwealth and across the globe. It does not depend on being tied up in a backward-looking, inward-facing, protection racket designed to prop up inefficient continental farmers and businesses. We want free trade with the EU, but we do not need to be members of it to have that.”

Martin Vickers, the MP for Cleethorpes who is also holding a mini-EU referendum, said Ukip had offered not to challenge him in exchange for a free run in neighbouring Grimsby. Vickers told the Mail: “From a purely selfish point of view, that would be quite welcome, but I can’t deliver it. Even if the local party was willing to do it, we’re a national party and we will have a candidate in every seat.” But Vickers said there was “absolutely no way, under no circumstances whatsoever” that he would defect.

Peter Bone, MP for Wellingborough, has denied planning to defect, although he followed Reckless and Carswell in holding a local EU poll in his constituency. Bone, in common with other Tory MPs holding the polls, has been advised by Chris Bruni-Lowe, who worked for Carswell before his defection, according to the Daily Mail.

Bone admitted that his mini-referendum was a “crib” of the one used by Reckless. But he insisted that he was not about to defect. Asked by the Daily Mail whether he was considering it, he said: “I deny that 10,000%. I have been a member of the Conservative party since I was 15. I believe we should have a pact with Ukip [but] I have never had any discussions with anyone in Ukip about defecting.”

John Baron. Photograph: Getty Images

John Baron, MP for Basildon and Billericay, another serial rebel who has been highly critical of David Cameron’s foreign interventions, is also high on the list of potential defectors.

The prime minister, who has been dismissive of Baron in the past, showed the Tory leadership was treading carefully with potential defectors when he made a point of lavishing praise on him in the Commons on Wednesday, when the MP called on the government to pay £25m to nuclear test veterans. “I pay tribute to my honourable friend who has been dogged in pursuit of this very important cause,” Cameron said.

Baron declined to rule out joining Ukip last month. He told Newsnight: “You should never say never in politics but the bottom line is my very strong preference is to stay within the Conservative party”.