David Cameron has authorised a poster campaign next week amid Tory fears that Gordon Brown is preparing to announce an election this autumn.

The new advertising will seek to neutralise Labour claims that Mr Cameron has no substance and does not believe in anything, according to allies of the Tory leader.

It forms part of a concerted effort to narrow a Labour poll lead that has opened up since Mr Brown entered No 10 in June and which might lead the Prime Minister to gamble on an early election.

Mr Cameron has made high-profile interventions on traditional Tory issues such as crime and immigration in recent days as he seeks to recover lost momentum before the party conference season. “We couldn’t have a situation with Brown going into party conferences with a ten-point lead,” one member of the Conservative leader’s inner circle told The Times.

Gordon Brown's Black Wednesday

The Northern Rock disaster has torn away any remaining credibility the Prime Minister had

BACKGROUND

• Sorry story tests Gordon to the limit

• Gordon, how wonderful, wise and talented am I?

• Brown’s brain and his hand are not always connected

• How 'cruel' schooling scarred Brown

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Senior Tories at the party’s headquarters are convinced that Mr Brown is planning an important announcement next week, and fear that it could be the election date.

The Tory leader’s publicity blitz, which has included hints of tax cuts and demands for a referendum on the European Union reform treaty, has led to claims of a “lurch to the Right”. The focus on immigration has caused disquiet among some of his most senior allies. Steve Hilton, Mr Cameron’s chief strategist, is said to be among those unhappy at the decision to draw attention to the subject.

Mr Cameron suffered a small setback yesterday when Arnold Schwarzenegger, the film star and Republican Governor of California, pulled out of appearing in person at the Tory party conference in Blackpool this month. He blamed “diary issues” and will instead speak to delegates via a video link.

The Conservatives will, however, take heart from the growing pressure on Mr Brown from within his own party to grant a referendum on the EU treaty that critics say is a constitution in all but name. Keith Vaz, a former Labour Europe Minister, became the latest senior Labour figure to demand that Mr Brown honour a manifesto pledge to hold a referendum on changes to the EU yesterday.

David Miliband, the Foreign Secretary, and Jim Murphy, the Europe Minister, sought to defend the Government’s position that the treaty does not require a referendum. Mr Murphy said the constitution had been “abandoned” and that Parliament was “the right place for ratification”. Mr Miliband denied that Labour was divided over an EU referendum: “We’ve made clear that following the June European Council, where the constitutional treaty was abandoned, it’s parliamentary scrutiny that’s the right way forward.”

Last night a No 10 source sought to calm speculation of a snap poll. “There is no election announcement next week, this is just a diversionary tactic in the face of the Tory meltdown.”

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