NICOLA Sturgeon and Jim Murphy fired up their General Election campaigns yesterday, with the First Minster asking No voters to back the SNP for the sake of a "home rule" Scotland, and the Labour leader warning a vote for any party but his would risk a second term for the Conservatives.

With polls showing the SNP poised to snatch dozens of seats from Labour, Sturgeon wasted no time putting the festive truce behind her, and went on the attack against her chief opponents this May.

In a message to SNP members, she said that after the polarised debates of the independence referendum, the election was a chance "to unite as a country" by sending as many SNP MPs to London as possible.

She said if Scots voted for "Westminster parties", those parties would think they were off the hook and backslide on delivering their "vow" of extensive new powers for Holyrood.

"On the other hand, if Scotland votes SNP, there will be no going back to business as usual," she said.

"Westminster will not be able to ignore Scotland and the promise of a powerhouse parliament that can create more jobs and protect our public services will have to be delivered.

"Our message this election reaches beyond those who normally vote SNP and those who voted Yes.

"If you voted No but support a home rule Scottish Parliament, a vote for the SNP is the only way to deliver it.

"Even if you don't normally vote SNP at Westminster, lend us your vote this time so we can hold Westminster to account and make Scotland's voice heard."

The SNP also unveiled its first election advert, which showed a swathe of tartan along the benches in the House of Commons and the slogan, "The more seats we have here, the more powers we'll have in Scotland".

However, the image showed the opposition benches, suggesting the SNP won't actually be in power.

A party insider said the picture was "simply an illustration" of the case for more SNP seats.

Returning to a key message of her party conference last November, Sturgeon said people should not believe Labour's argument that a vote for the SNP would help keep David Cameron in office.

"They will trot out the same old mantra about voting Labour to keep the Tories out," she said. "That argument is an insult to the intelligence of the Scottish people."

She said Scotland voted Labour four times in a row in the 1970s, 80s and 90s, and still got a Tory government, adding: "If enough people in England vote Tory again in May, a Tory government is what we'll get. Or worse, a Tory/Ukip government."

The Conservatives won 307 seats in 2010, 298 of them in England, so a Tory majority of 326 would require Cameron to win an extra 28 seats in England - a feat no poll has even come close to predicting.

Sturgeon said that if there was a Conservative government, Scotland would need "strong SNP MPs to stand up to the Tories and fight Scotland's corner".

While in a hung parliament, a large SNP group could hold the balance of power and extract more powers from a Labour government, she stressed the SNP would never support a Tory administration.

Meanwhile, trailing a speech he will give in Edinburgh ­tomorrow, Murphy urged Scots to vote Cameron out of Downing Street and ignore SNP arguments about electing SNP MPs to stand up to the Tories.

He said: "I know the last thing SNP voters want is a Tory government but David Cameron may end up as the accidental victor if Scots vote SNP. It is a fact the SNP simply cannot ignore … that any seat they take off Labour in the General Election makes it less likely that Labour will be the biggest party, and more likely that David Cameron will get to form the next government.

"The nearer we get to the ­election, more and more Scots will be asking a simple question: what is the point of sending a Nationalist MP to protest against a Tory government when you can send a Labour MP who will replace a Tory government?

"This year's General Election isn't about sending a message to the Tories; it's about sending the Tories packing."

Murphy said Cameron would drag the UK "back to 1930s public spending levels with underfunded tax cuts", and the country was confident enough to vote for a progressive Labour alternative.

A Scottish Conservative spokesman said: "The choice facing people this year is whether to keep on track with economic recovery or to pick a chaotic alternative which puts a weak Labour Party in power. The fact is that the Scottish Conservatives are the only pro-UK party in Scotland which will keep the economy secure and keep Ed Miliband out of Downing street."

Labour election ­co-ordinator Douglas Alexander yesterday suggested his party might be outspent "by as much as three to one" by the Tories. However, parties often bemoan a lack of spending power to encourage extra donations.

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