A senior member of the cabinet has denied the Conservatives are in a panic over the Rochester and Strood by-election as the party triggered a huge blitz of the constituency.

In a major offensive, the party sent in hundreds of activists today with a claim that every home would get a campaign pamphlet over the weekend.

The unprecedented scale of activity was seen as the official launch of the Tory campaign, triggered by the defection of Mark Reckless to Ukip.

It came even though the party has yet to choose its candidate and will not do so until next Thursday after a 'primary' postal ballot open to all voters.

Three cabinet members joined the campaign today - Chancellor George Osborne, home secretary Theresa May and justice secretary Chris Grayling.

Mr Grayling shrugged off a comment from Ukip leader Nigel Farage, who said the Conservatives were "trying too hard".

But he acknowledged it needed to win over undecided voters, saying: "This is a by-election that is eminently winnable but we have to go out and make the case.

"If we weren't doing this, Nigel Farage would be saying 'oh, they can't be bothered'. We are doing what we have done in every by-election.

"Actually Nigel Farage should be worried that we have a real campaign going here to make sure we keep this seat.

"I am very confident that this is a seat we can win. It does not mean we will win it but we can win it. We know it is a tough battle."

He said the government was right to make immigration the focus of its renegotiation of membership of the EU.

Anna Firth, one of the two Tory candidates for Rochester, said she favoured a points based system for EU member states.

Mr Grayling said: "We are going to need some kind of mechanism to exercise control over our borders.

"We have seen over the last 10 to 15 years a very big wave of immigration. It is not about race, it is not about nationality.

"It is about how many school places we have got; it is about how much capital investment we have got in our hospitals.

"There are limits to the number of people who can come and live in this country. What we are now focusing on as part of our renegotiation is to really press the issue."

Ms Firth and Kelly Tolhurst, the other Tory hopeful, have also been out canvassing.

The day of action follows an appearance by PM David Cameron in Strood on Thursday - said to be one of five visits he plans.

The by-election follows the defection of Mr Reckless to Ukip last month.

Meanwhile, Britain First has announced it is to contest the seat. It will be the far-right political group's first Parliamentary election.

Deputy leader Jayda Fransen has been selected as its candidate. The group has been actively campaigning against the construction of a mosque in Railway Street, Gillingham.

It says members made the decision at an "emergency meeting" yesterday to "extend our campaign against the mega mosque by standing a candidate in this by-election".

According to its website, the campaign "will begin immediately with more protests, marches and days of action".

Voters go to the polls on November 20.