Without a “clearer narrative” on immigration, the Conservatives would not win
back enough voters from Ukip to achieve a Commons majority, he warned.

The Tory leadership has privately conceded that Mr Cameron has no hope of
winning more seats than Mr Farage in the European Parliament elections in
May.

Many inside the party also fear that there is no chance of Mr Cameron now
delivering on his promise to reduce net migration to the “tens of
thousands”, after figures showed the number of immigrants rose last year.

Dr Fox made the comments as a leaked letter emerged in which the leader of 34
Tory councillors in Guildford accused Mr Cameron of undermining the party’s
chances of winning the next election.

Stephen Mansbridge told Mr Cameron that the Tories were being “placed in an
impossible electoral position through your government’s policies”. The
letter was backed by councillors and was being passed to No 10 by Anne
Milton, a local MP and government whip.

At the same time, Eurosceptic MPs warned that the Prime Minister’s
“vacillation and procrastination” on whether to adopt a tougher
anti-European policy would allow Ukip to take votes from Tories.

Bill Cash, who chairs the Commons EU scrutiny committee, said this could cost
the party “50 or 60 marginal seats”.

Dr Fox, who was Mr Cameron’s first defence secretary, issued his strongest
warning yet to the Prime Minister that a radical change of direction was
needed.

He said that “current betting” suggested that Ukip were favourites in the
European polls on May 22.

“If they do well, many will point to the successes of previous minor parties
that did well in the Euro elections only to fail at the next general
election. This could be dangerous complacency, especially for the Tories,”
he said.

The Tory response must not be to attempt to outflank Ukip from the Right, the
former Cabinet minister writes.

“The correct response is to set out a positive vision, clear philosophy, and
definable objectives,” Dr Fox said.

In particular, he calls for a radical new policy on immigration, moving away
from the party pledge to cut net migration to the tens of thousands by next
year, which looks ever more impossible to meet.

Figures last week showed that net migration rose by 58,000 to 212,000 in the
12 months to last September, with the increase due to more workers from the
EU.

Dr Fox said Tories should win back voters who have switched allegiance by
pointing out the “unavoidable consequences” of a vote for Ukip.

“If the Tories are to bring back enough of these voters to win an overall
majority at the election, then there needs to be a clearer narrative on
immigration, stressing not only the need to restrict numbers, but also to
determine which individuals, with what skills, enter our country.

“While Conservative policy has concentrated on getting down the net migration
numbers, it is actual numbers that affect school places, housing and health.
The Conservatives must ditch this statistical nonsense.”

In what will be seen as a coded criticism of the Prime Minister and his
allies, Dr Fox calls for an end to the “name-calling” and the accusations
that Ukip activists are “cranks” or “crackpots”.

Mr Cameron famously described Ukip as a party of “fruitcakes, loonies and
closet racists”.

Mr Cameron is also facing growing concern over the rise of Ukip from
grass-roots activists outside Westminster.

In a letter to him, the leader of Guildford council said he feared the borough
would lose its Tory majority for the first time in 12 years and that Mrs
Milton would be defeated at the election.

Stephen Mansbridge said there was huge local opposition to the “excessive
number of new homes” being forced on the area’s green belt by government
policy.

“We have lost many Conservative party members — indeed whole branches of the
local association — due to various government policies, and Ukip won over 20
per cent of the vote in the local elections last year in Surrey,” he said.
“Immigration, the EU and gay marriage are frequently given as reasons for
this.”

The Conservatives’ manifesto for the European polls will be largely a
restatement of existing plans, including the promise of a referendum in 2017
on Britain’s membership of the EU.

The party has shelved plans to make reform of human-rights law the centrepiece
of the European election campaign because senior figures regard this as a
waste of a potentially popular reform.