Scottish nationalists are preparing for landslide election gains at the expense of Labour next month but also holding out the offer of a pact that could put the centre-left party in power.

"Scotland's voice at Westminster has always been very quiet, in fact it's been completely muted because the strings have been pulled by UK Labour," said Carol Monaghan, an Scottish National Party (SNP) candidate in Glasgow.

"People don't want that any more," she added.

Labour won 41 out of 59 seats in Scotland in the 2010 vote, but polls suggest the majority of these will pass to the pro-independence SNP on May 7.

Without big wins in Scotland, Labour has little chance of winning a majority in Britain's 650-seat House of Commons -- but neither does Prime Minister David Cameron's Conservative Party, leaving the election wide open.

"If Labour weren't losing ground in Scotland... it would be pretty obvious that they were the only party capable of forming a government," said John Curtice, professor of politics at Strathclyde University.

"The fact that they are at risk of losing heavily in Scotland is what's helping to turn this election into such an uncertain and unpredictable contest."

But the SNP surge could improve, not hinder Labour leader Ed Miliband's chances as the party has indicated it could support a minority Labour government to keep Cameron out.

"I don't want David Cameron to be prime minister, I'm offering to help make Ed Miliband prime minister," Sturgeon said in a televised debate on Tuesday.

- Resentment against Labour -

In the central Scottish town of Cumbernauld, Labour MP Gregg McClymont won 57 percent of the vote at the last election but is fighting to keep his seat amid polls showing a major swing to the SNP.

"It's certainly going to be a tight contest, there's no denying it," he said, pushing leaflets through doors on a housing estate during a spring hail storm.

The grey, low-rise houses here are built in a warren of alleys strewn with discarded shopping trolleys and the odd forlorn flower bed.

Many voters seem receptive to Labour's policies on the key issues of education and the state-run National Health Service, and McClymont remains upbeat.

But there is still resentment against Labour, which was in government in Britain between 1997 and 2010.

The party has been demonised by the SNP as being too similar to the Conservatives and was widely blamed for the financial crash of 2008.

The SNP has in recent years pitched beyond its nationalist base to traditional Labour voters with a message of a fairer, more equal Scotland in charge of its own affairs -- with significant success.

The party has run the devolved government in Edinburgh since 2007, and in the 2011 Scottish parliamentary elections won an impressive 45 percent of ballots cast.

The "Yes" campaign secured a similar proportion of the vote in September's independence referendum, and that enthusiasm now looks set to translate into SNP success at Westminster.

- Voice in Westminster -

Glasgow has long been solid Labour territory but the party could be set to lose all but one of its seats, according to polling.

In the north-west of the city, Monaghan -- a physics teacher moved to enter politics after the referendum -- looks set to overturn a Labour majority of 19,000.

It helps the SNP's campaign that Labour campaigned with the Conservatives against independence -- the Tories are deeply unpopular in Scotland, and have just one MP here.

"I think having a stronger SNP voice in Westminster is generally a good thing to shake up the big, larger parties," said Stewart Cunningham, a 33-year-old PhD student who is switching from Labour to the SNP.

Labour has declined to say whether it would take up its old enemies the SNP's offer to do some kind of post-election deal, only ruling out a formal coalition and saying there would be no SNP ministers in a Labour government.

The two parties share some policies -- they would both raise the top rate of income tax and the minimum wage, and oppose the referendum that Cameron has promised on Britain's membership of the European Union.

For Curtice, this means that, despite its losses the Labour party has a "friend in the SNP" that Cameron lacks.

"And that, to some degree, other things being equal, does tip the odds in favour of Ed Miliband being the next prime minister," Curtice said.

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