Two Conservative MPs are being touted as possible defectors to Ukip as a new poll is released giving Nigel Farage’s party a 13-point lead over the Tories in the Rochester and Strood by-election on 20 November.

One is John Baron, MP for Basildon and Billericay, considered a very safe Tory seat until now, who was named by the prominent Tory commentator Iain Dale on Sky News last night as a possible deserter.

Dale, taking part in a late-night newspaper review, was reluctant at first to name Baron but then agreed to do so, because of what he described as growing speculation in Tory circles.

The other is Conor Burns, MP for Bournemouth West, another safe Tory seat – though Ukip came a respectable fourth there in the 2010 general election, as opposed to fifth behind the BNP in Basildon and Billericay.

Reports say Burns has been seen chatting with Farage at Westminster. For most loyal Tories, Farage is toxic and to be seen talking to him politely is enough to get the jungle drums pounding.

Neither Baron nor Burns has yet to respond, but when Baron was asked on Newsnight in the wake of Ukip’s Clacton by-election victory if he might defect, he said: “You should never say never in politics.”

Burns’s most recent word on the subject was to say he had had a “good chat” with Farage but did not intend to leave the Conservatives.

The speculation is hotting up just as a new poll points to an easy victory for Ukip in the Rochester by-election caused by the defection of Tory MP Mark Reckless. This is despite the Tories “throwing the kitchen sink” at saving the seat.

The survey by ComRes shows 43 per cent of voters are planning to back Reckless, with just 30 per cent saying they will vote Conservative, 21 per cent Labour, three per cent Lib Dem and two per cent Green. The Ukip lead is four points higher than in a Survation poll conducted earlier this month.

It’s important to note that the ComRes poll was commissioned by Ukip and its timing is clearly designed to upstage the Tories’ announcement of their candidate this evening.

But that does not make the poll any less reliable and it should not detract from the historic size of the victory that appears to be on the cards at Rochester and Strood.

For Cameron's team, just as worrying as Ukip's strong lead is ComRes's finding that 66 per cent of local people believe the Tories “are coming across as desperate” by sending so many politicians to the Kent constituency to canvas.

Cameron has promised to visit the seat five times before polling day: that may have to be scaled down if showing his face there proves counter-productive.

Ukip MEP Patrick O’Flynn told the Daily Express: “It is particularly good to know that the prospect of having hundreds of Tory MPs descending upon them is not one that the voters are regarding in a positive light and one can hardly blame them for that.”

Candidate Mark Reckless said: “If I win here, Cameron can expect a leadership challenge.” He added: “The opportunity for Labour voters to possibly bring down Cameron by voting for me as the Ukip candidate is attracting a lot of support.”

What’s exciting Ukip is that Rochester and Strood was never a target before Reckless made his move: it ranks a mere 271 in Farage's list of “most winnable” seats.

If Ukip win on 20 November, the party would be in a “very different place”, said Farage during a visit to the constituency last week. “This is a very serious, important by-election. I think it's the most important in British politics in over 30 years.”

The Ukip bandwagon was given a further shove yesterday by Jean Claude-Juncker, the new EU Commission president, who backed Manuel Barroso, his predecessor, in warning that Cameron’s plan to put a brake on EU immigration would not be legal under EU law.

Juncker said he would not compromise in an “irresponsible way” on rights that date back to foundation of the EEC.

Cameron will face questions about his immigration plans on the margins of an EU summit in Brussels opening tonight which will formally discuss climate change, economic growth, the Ebola crisis and Ukraine. All the signs are that – once again - Cameron will have to eat humble pie.