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The Tories should be much more worried about Labour leader Ed Miliband than UKIP's Nigel Farage during the general election campaign, former Conservative Party Chairman Lord Patten has said.

Mr Miliband was "highly intelligent" and a "good debater", the peer told BBC Radio 4's Week in Westminster.

There have been suggestions that David Cameron's chances of winning in May depend on squeezing the UKIP vote.

But Lord Patten said Mr Farage "is probably a balloon which is deflating".

His comments come in a week in which Mr Cameron vowed not take part in TV debates ahead of the general election unless the Green Party is also included.

At Prime Minister's Questions on Wednesday, Mr Miliband called Mr Cameron's refusal to take part a "pathetic excuse".

Lord Patten told the BBC: "I wouldn't be worried about the Farage factor; I'd be much more worried about the platform it gives Ed Miliband."

He said he was concerned that during the election campaign the Labour leader "might come across a lot better" than the press says he is.

Image caption Lord Patten said he believes Mr Cameron should not have taken part in the 2010 debates

Mr Miliband, Mr Farage and Lib Dem leader Nick Clegg have urged broadcasters to press ahead with televised debates before the 7 May poll even if Mr Cameron refuses to take part. The three leaders have also written to the prime minister saying it would be "unacceptable" for him to refuse to appear.

But at Prime Minister's Questions, Mr Cameron said Mr Miliband was "chickening" out of facing the Greens and all "national parties" must be represented.

'Difficult to stop'

The BBC's political editor Nick Robinson said Mr Cameron was unwilling to do anything that gives Nigel Farage a boost.

He had long decided the debates at the 2010 election had sucked the life out of the campaign and given a boost to his opponents, our political editor said in a blog entry.

Under plans put forward by the BBC, Sky News, ITV and Channel 4 in October, the pre-election live TV debates would include the Conservatives, Labour, Liberal Democrats and UKIP.

Mr Cameron would take on Mr Miliband head-to-head in one debate, another would feature Mr Cameron, Mr Miliband and Lib Dem leader Mr Clegg, and a third would also include UKIP's Mr Farage.

On the Week in Westminster, Lord Patten said Mr Cameron should not have taken part in televised leaders' debates before the last election, because "once you start doing them, they are very difficult to stop".

UKIP secured two by-election victories over the Conservatives - in Clacton and Rochester and Strood - last year.

Responding to Lord Patten's view of the threat from Mr Farage, a UKIP spokesman said the opinion polls suggested the party's popularity "wouldn't descend any time soon".

Conservative Party chairman Grant Shapps said the TV debates could go ahead if the Greens were included.

He told the Times there was "still time for this all to be organised and I think it will".

"What people would appreciate is a common sense debate between either the two guys who could be prime minister or everybody who is standing nationally."

The Week in Westminster is on Radio 4 at 11:00 GMT