William Hague will this week dramatically change strategy and call on voters to give Tony Blair a fright on Thursday.

As a raft of opinion polls point to a Labour landslide, the Conservatives are to rethink their approach ahead of Thursday's general election.

According to Sunday's polls, Labour's lead varies between 16 and 23 per cent - pointing to a majority of at least 160.

In a bid to avoid a meltdown on Thursday, the Conservatives are set to dramatically change strategy, calling on voters to "cut Labour down to size" by reducing Blair's majority.

A poster, unveiled by the Conservatives on Sunday, shows a picture of a grinning Tony Blair with the caption: "Go on - Burst his Bubble."

Recognising that a defeat is almost now inevitable, the Conservatives are hoping to persuade voters that a second landslide victory would be bad for parliament and democracy.

Speaking on Sunday, Hague said Labour would abuse a big majority. "We have never had a government that has so sidelined parliament, so arrogantly abused the democratic institutions of this country. That is how they have behaved when they had a landslide the last time," he told Breakfast with Frost.

The party is also shifting its emphasis on the issues of the single currency and asylum onto health, education and police numbers.

Left-wing Conservatives, including Ken Clarke, Chris Patten and Sir Leon Brittan, believe Hague made a serious tactical error in focusing on tax and the euro for the first three weeks of the general election campaign.

However, the Conservatives are taking heart from new research by Plymouth University's Elections Centre which has used recent council by-election results to predict a reduction in Labour's majority to 147 seats.

Ann Widdecombe, the shadow home secretary, denied that the Tories' new strategy signalled that the party was preparing for defeat.

She told Sunday with Adam Boulton that although Tony Blair "promises the earth, he delivers very little".

"He poses as ruling a party that is purer than pure that blatantly obviously hasn't been. Most people out there are pretty fed up with it," she said.

Privately, however, Conservative sources are admitting that William Hague is fighting to save his seats.

But the Northern Ireland secretary, Dr John Reid, said Labour was not taking a single vote for granted.

He told GMTV on Sunday: "We are only there on the privilege of trying to change our country by virtue of the support of the people of Britain. We will not take one voter for granted."

He repeated Tony Blair's view that the only poll which mattered was Thursday's. "There is no landslide, indeed there is no vote until next Thursday," said Dr Reid.

He was dismissive of the Conservatives' campaign, saying it was "bizarre, bordering now on the pathetic".

Labour has also accused the Conservatives of talking up Labour's chances in a bid to make the election look more certain than it is.

Tony Blair said the Tories were trying to boost their chances in what he described as "a last desperate throw of the dice".