And an authoritative study finds that unless party leader David Cameron raises the game in rebuilding its activist base, many former Tory strongholds such as Harrogate, Sheffield Hallam and Leeds North West will never turn blue again.

In a new wide-ranging analysis of local and General Election performances in the North of England, urban politics guru Tony Travers, of the London School of Economics, concludes that even if the Tories do well at the next election, the most they can hope for is a hung Parliament.

His analysis compares the Tories' performance today with the party following years of Labour rule during the 1970s and finds that it is doing nowhere near as well as it should be.

Prof Travers said: "If you look at the late 1970s at the end of the Callaghan government the Tories dominated Bradford, Calderdale, Kirklees. They were in control of Leeds in their own right.

"But today they need the support of other parties to control Leeds and Bradford, and Westminster seats that they either already held or were marginal are now not even remote possibilities.

"Look at Leeds North West – it used to be held comfortably by the Conservatives with up to 45 per cent of the vote in the 1970s . Now they're in third place, and you get a similar picture in other parts of Yorkshire and Humberside.

"Sheffield Hallam was a safe Tory seat and now it's hard to see how they're going to take that back."

Opinion polls may be showing the Tories ahead, said Prof Travers, but if they really were doing well they should be regularly hitting the 45-point mark rather than loitering around 40 points. "It's metropolitan Yorkshire that's stopping them getting above that 40 per cent level," he added.

Mr Cameron's arrival as party leader two years ago led to a sea-change in attitude at Tory headquarters towards the North of England and its electoral importance. It was followed by the establishment of the Northern Board earlier this year, chaired by William Hague and given the job of co-ordinating the party fightback.

A new regional campaign office in Bradford with a team of full-time Yorkshire strategists and additional resources has also been put in place.

But Prof Travers maintains that rebuilding the activist base in many places, let alone the voter base, "will be a long hard slog and take years" and will not happen by the next General Election in 2009 or 2010.

"The Tories simply aren't winning in all the places that they used to," he said. "Unless something changes, the party's relative weakness in Yorkshire will deny the Conservatives an overall majority which they should otherwise be seriously contemplating.

"You don't have to be a fantasist to think that the Tories will be the biggest party in Westminster, but a few seats in West Yorkshire could make the difference between David Cameron becoming Prime Minister without doing deals with the Liberal Democrats and assorted nationalists."

Shipley MP Philip Davies – the only Tory to win a Westminster seat in West Yorkshire since the 1992 General Election – said: "West Yorkshire is clearly an absolutely crucial battleground at the next election and it's essential that we do better than we've done in the recent local elections if we're going to win the seats we need.

"But I do think that the political landscape has changed immensely since May and I think that the next local elections will show how it's changed."

Labour's Denis MacShane, the MP for Rotherham, said yesterday: "The moment you travel north of Watford you enter Tory-free England.

"David Cameron's Old Etonian Notting Hill charm may work in London and the South-East but it's utterly disconnected from the real problems of real people.

"And William Hague, who is supposed to be devising the Tory fightback in the North, spends every waking moment talking about Europe, which is important for Eurosceptic obsessives but not something that the vast bulk of voters want politicians to address."

But last night Mr Hague said: "We are already dramatically scaling up our efforts in Yorkshire and in particular West Yorkshire, and this year we have opened our new campaign centre.

"We have excellent candidates in place and believe we can make many gains at the next election."