LORD Mandelson has made a direct appeal to non-Tory voters in the Westcountry to support the Liberal Democrats in a bid to hold back a Conservative landslide in the region.

The Business Secretary and key architect of Labour election strategy told the Western Morning News that the Lib-Dems "have more in common with Labour than with any other party".

Only Labour could form a government and deliver on Lib-Dem aspirations, he added.

The pitch to Westcountry voters comes as the Lib-Dems meet in Birmingham today for their spring conference, the last major gathering before the General Election expected on May 6.

Lib-Dem leader Nick Clegg has been the focus of attention from both the main parties, as opinion polls suggest there could be a hung parliament, with the third party dubbed "the kingmaker".

He faces a potential backlash from the party rank and file over reports he would be more likely to strike a formal deal with the Tories in the event of a hung parliament.

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This week Mr Clegg appeared to focus on highlighting his Conservative credentials, praising former premier Margaret Thatcher for taking on the vested interests of the unions. Mr Clegg has also made clear it would be difficult for the Lib-Dems to prop up a Labour minority government if voters reject Gordon Brown at the ballot box.

One in 10 of the Conservatives' target seats needed for a majority in Cornwall, Devon and Somerset, are Tory/Lib-Dem battles. Labour's hopes of securing an historic fourth term depend on persuading thousands of Lib-Dem supporters in areas like the Westcountry not to switch allegiance to the Conservatives.

Asked what his message would be to Westcountry Lib-Dem supporters thinking of switching to the Tories, Lord Mandelson said: "My appeal is to all progressives in the country – to pause and reflect on where their values lie, and to recognise that they have more in common with Labour than with any other party.

"And that the difference between Labour and the Liberal Democrats is we can form a government and deliver the values progressive people hold."

The Lib-Dems are fighting battles on two fronts. In regions like the Westcountry they must see off the threat of a resurgent Tory party, but in northern marginals, the Lib-Dems are locked in a battle with Labour, and Lord Mandelson also sought to persuade voters in these areas to stick with the Government.

He also admitted Labour remain the "underdogs" in the coming election after the country suffered "a heck of a beating" because of the global financial crisis.

"We start from behind, but what I see is that many people in the country are moving towards the Tories, but as they get closer to them, they baulk at opting for them," he said. "Behind the fluffy centralist language of their leader, Tories haven't changed one jot."

Mr Clegg has spelled out four "tests" he will set for Labour and the Conservatives if they are to seek his party's support in a hung Parliament following the election. They include reform of the tax system to lift four million people earning £10,000 a year or less out of income tax altogether; a "pupil premium" to target extra education spending at the most disadvantaged children; a greener economy and voting reform for Westminster elections.