Swuhwwx Tony Blair will enter the election campaign later with an attack on David Cameron's pledge to hold a referendum on Britain's EU membership.

The former PM will accuse Mr Cameron of trading national interest for political advantage under pressure from UKIP and anti-European Conservatives and media.

Mr Blair will say Labour's Ed Miliband has shown "real leadership" by resisting pressure over a referendum.

But the Tories said his intervention was a sign of Mr Miliband's "weakness".

Mr Blair won general elections as Labour leader in 1997, 2001 and 2005, and stood down as prime minister in 2007.

BBC deputy political editor James Landale said Mr Blair had "largely stayed out of British politics" since then - but Labour hoped he still had "enough lingering stardust to appeal to some voters".

In other election developments on Tuesday: The Conservatives and Lib Dems disagreed with Labour

figures suggesting it is harder to see a GP in England now than it was before 2010

Nick Clegg set out how the Lib Dems would use the proceeds from a crackdown on tax evasion to fund income tax cuts

David Cameron will campaign in Scotland , Wales, Northern Ireland and England in a single day

Research for BBC Scotland  suggested voters in Scotland favour targeted public spending ahead of efforts to eliminate the deficit or cut taxes

Nigel Farage dismissed calls from Mr Cameron for UKIP supporters to "come home" to the Conservatives

The Green Party says a pledge of a £72 a week "citizens' income" for every British adult will be in its manifesto but will take more than five years to introduce

'Too important'

Mr Cameron has pledged to renegotiate a "better deal" for the UK in Europe and to stage a referendum on the UK's membership in 2017.

Policy guide: EU

This election issue includes the UK’s membership of the European Union and its negotiating position.

Compare parties' policies

But speaking in his former constituency of Sedgefield in County Durham later, Mr Blair will say a possible EU exit would leave a "pall of unpredictability hanging over the British economy".

"And the oddest thing of all about David Cameron's position? The PM doesn't really believe we should leave Europe; not even the Europe as it is today," he will say.