Tory leader Michael Howard has mounted a scathing attack on the the UK Independence Party.

The speech came as Conservative HQ signalled that its party's campaigners should characterise UKIP candidates as "Little Englanders" and "cranks and political gadflies".

Tory strategists fear that their traditional supporters may be won over by UKIP's message.

A 14-page briefing paper on UKIP, drafted by Conservative Research and Development and leaked to the Times newspaper, advises party activists that as a minor party UKIP stands no chance of securing change in Europe.

In an address which came after four Tory peers announced they were backing UKIP, Howard defended the Tories' policy on Europe.

"The European parliament has important powers," he said during a visit to Southampton.

"Its members help to decide the kind of laws that are made in the European Union. They can influence these laws for better or for worse.

"Or they can abdicate their responsibility and not vote at all – even on matters that are of vital importance to the countries they represent. Here in Britain we face a clear choice.

"At one extreme there are the candidates from the UK Independence Party. They represent a party that wants to pull out of the European Union altogether. They have frequently failed to vote in the European parliament on issues that are vital to Britain.

"At the other extreme are Labour and the Liberal Democrats - who want to transfer even more from Britain to Brussels, setting Europe on the path to a single European State. The Conservative Party rejects both these extremes."

Engagement

Howard said that his policy of critical engagement with Europe is the best way to ensure Britain's interests are defended.

The Conservative leader set out his party's position on the EU, saying that only the Tories offer a place in Europe without giving up any more powers to Brussels.

"Britain's interests are best served by staying in Europe - but by using our influence to make the EU confront its failings and become more tolerant," he said.

"That is what the mainstream majority in Britain want - and that is what a Conservative government will give them.

"But the fringes at both ends of the European debate are united in one thing. Both give the British people the defeatist message that we cannot have a flexible Europe. They argue that we have to put up with what we are given or leave altogether. Both sides peddle this myth for their own political ends. And they are both wrong.

"Since I became leader of the Conservative Party, I have argued the case for a 'live and let live' Europe. We do not want to stop countries within the EU integrating more closely if that is what they want to do - as long as they do not try to force us to do what we do not want to do."

'Waste'

The attack is being seen as fresh evidence that the mainstream political parties fear a strong performance for the anti-EU camp on June 10.

Opinion polls suggest UKIP, which has recently secured the endorsement of celebrities including Joan Collins and Robert Kilroy Silk, could push the Lib Dems into fourth place.

But Howard warned Tory sympathisers that a vote for UKIP will be a "waste".

The Tory chief claimed that eurosceptic criticisms of his policy are wrong.

"Some say 'that sort of Europe is not on offer'. I reject that defeatism," he argued.

"It is on offer from the Conservative Party. And it makes sense - not only for countries like Britain who do not want to transfer any more power to the EU. But also for those countries who want to integrate more closely but feel held back by other member states.

"The Conservative vision is not just about what Britain wants from the EU, it is about what all the nations of Europe want from the EU. That is why it is right. That is why it is in their interests to accept our vision of a more flexible and tolerant Europe that respects diversity.

"And let me make this clear," he will add. "Only the Conservative Party can deliver this Europe. Not the Labour Party. Not the Lib Dems. No other party.

"So if you share our vision for Europe, don't waste your vote."