David Cameron visited the Rochester and Strood by-election today

David Cameron has warned voters that victory for Ukip in the Rochester and Strood by-election would help establish the party.

On a visit to the Kent constituency where defector Mark Reckless is on course to crush the Conservatives, the Prime Minister dismissed the party as being about 'stunts and politics'.

‎Senior Tories had declared the contest a 'must-win' but‎ Mr Reckless has a 15 point lead over his former party according to the latest opinion poll.

Yesterday, Mr Cameron, who had pledged to 'throw the kitchen sink' at the attempt to hold the seat and halt the Ukip surge made his third of five expected visits ahead of the November 20 poll.

Speaking at Chatham Docks where he toured a company making parts for the Crossrail project alongside Tory candidate Kelly Tolhurst, he said: ‎'I think Kelly is the strongest local candidate who will work the hardest for the seat.

'If you vote for Kelly it's about you and your new MP and the work she'll do for you.

'If you vote Ukip, it's not about you, it's about them.

'It will be about stunts and politics and trying to make a thing out of Ukip rather than trying to deliver for the people of Rochester and Strood.'

Mr Cameron added that a Ukip win would 'effectively give them a boost for their campaign'.

Hours after Mr Cameron's visit, Ukip leader Nigel Farage appeared at a rally alongside candidate Mr Reckless.

Ukip is odds on favourite to win the by-election, which was triggered after Mr Reckless defected from the Tories.

A poll published on Friday showed Ukip had widened its lead over the Conservatives by six points since an identical survey a month earlier, suggesting the huge Tory effort to keep the seat is failing to gain traction.

There are warnings that the Prime Minister could face a leadership challenge if the Conservatives fail to win.

The Prime Minister accompanied the Tory candidate Kelly Tolhurst (left) at the Crossrail site in Chatham, Kent

Mr Cameron said a win for Ukip in Rochester would boost Nigel Farage - seen wiping away a tear at the 'Seas of Red' poppy exhibition in London today

Former leadership contender David Davis was last week reported to be taking soundings about a possible plot to depose Mr Cameron if the seat is lost.

Mr Davis is said to have told fellow MPs that there is a 'window' of opportunity to organise a vote of no confidence in Mr Cameron between the by-election and Christmas.