Nicola Sturgeon is to warn Prime Minister David Cameron that "Scotland's voice has to be heard" after the SNP comprehensively routed Labour north of the border, winning an historic 56 Westminster seats.

While Mr Cameron pledged to give Holyrood "important powers over taxation", the Conservative leader does not appear to be offering any substantial new devolution.

He spoke after a watershed General Election left the UK divided, with the Tories winning an unexpected majority across the UK, but north of the border the SNP saw its tally of MPs surge from six five years ago.

Labour, which had taken 41 seats north of the border in 2010, was left with just one Scottish MP, with Scottish party leader Jim Murphy and election campaign chief Douglas Alexander among those who lost their seats.

While Ed Miliband announced he is stepping down as UK leader of the party, Mr Murphy insisted he will stay in his job in Scotland in a bid to rebuild his ailing party.

In an unprecedented night for the SNP, it took all seven of the seats in Glasgow, Scotland's largest city, with shadow Scottish secretary Margaret Curran among the losers there.

Former leader Alex Salmond was returned to Westminster as the new MP for Gordon after seizing the constituency from the Liberal Democrats.

Senior figures from the Lib Dems were also ousted in the nationalist landslide, with Danny Alexander, who had been chief secretary to the Treasury, and former party leader Charles Kennedy both ejected from the Commons.

Ms Sturgeon's party won 50% of the votes cast in Scotland, compared to just 20% in 2010. In comparison Labour saw its share of the vote fall to 24%, with the Conservatives on just under 15% in Scotland and the Lib Dems on 7.5%.

Labour's Ian Murray managed to retain his Edinburgh South seat in the face of the SNP tsunami, as did Liberal Democrat Alistair Carmichael, who held on to Orkney and Shetland with a reduced share of the vote.

David Mundell, who was Scotland's only Conservative MP in 2010, is still the single Tory representative north of the border.

As the results came in Mr Salmond declared that the ''Scottish lion has roared''.

Meanwhile Ms Sturgeon said: "The political firmament, the tectonic plates in Scottish politics have shifted. What we are seeing is a historic watershed."

The SNP leader, who travelled to London today to take part in the VE Day commemorations, said she was "deeply disappointed that Labour wasn't strong enough to beat the Conservatives in England".

But she added: "Given that we are looking at a Tory majority government, it is all the more important that Scotland is strongly represented by a big team of SNP MPs.

"The other point to make, and it's a point I'll make directly to the Prime Minister, the government cannot ignore what happened in Scotland last night.

"There was an overwhelming vote for Scotland's voice to be heard, for an end to continued austerity, and those issues which we put so firmly at the heart of the campaign we now intend to put firmly at the heart of the Westminster agenda.

"SNP MPs are there to stand up for Scotland, it is inconceivable that a government would ignore the democratic will of the Scottish people, which was expressed very, very clearly last night."

The First Minister continued: "It was Labour's job to beat the Conservatives in England, and Labour hasn't come close to doing that, even if Labour had won all of the seats they held in Scotland they still wouldn't have beaten the Conservatives."

She added: "I have no doubt I will speak to the Prime Minister in early course, and I will be making it clear that Scotland's voice has to be heard. That's what the people of Scotland voted for last night."

After returning to Downing Street, Mr Cameron said he would "stay true to my word" and implement plans for further devolution that have already been drawn up "as fast as I can".

He stated: "Governing with respect means recognising that the different nations of our United Kingdom have their own governments as well as the United Kingdom government.

"Both are important and indeed with our plans, the governments of these nations will become more powerful with wider responsibilities.

"In Scotland, our plans are to create the strongest devolved government anywhere in the world, with important powers over taxation."

Liberal Democrat Danny Alexander, who was chief secretary to the Treasury in the coalition, was the most senior member of the government to lose his seat as Inverness, Nairn, Badenoch and Strathspey fell to the nationalists.

With some constituencies showing swings to the SNP of more than 30%, Douglas Alexander, Labour's election campaign chief and shadow foreign secretary, was the first big scalp of the night.

Student Mhairi Black, 20, beat the former government minister in Paisley and Renfrewshire South to become the youngest MP in the House of Commons since 1667.

In Kirkcaldy and Cowdenbeath, which had been the safest Labour seat in Scotland, the SNP easily overturned a majority of more than 23,000 to capture the constituency which had been held by former prime minister Gordon Brown, who had stood down from Parliament.

Afterwards a defiant Mr Murphy rejected calls for his resignation, arguing that Labour in Scotland had been ''overwhelmed by history and by circumstance''.

He said the election campaign had been ''the biggest challenge in our 127-year history'', coming in the wake of last year's independence referendum and the SNP's back to back victories at Holyrood in 2007 and 2011.

Mr Murphy insisted: ''As leader I wanted to meet these challenges and I still do.''

But with the Scottish Labour leader now not holding elected office at either Holyrood or Westminster, questions will be asked about how long he can continue in the role.

Mr Murphy was elected to the job just five months ago after his predecessor, Johann Lamont, quit, accusing the party in London of treating Scotland like a ''branch office''.

Asked if he still believes he could be first minister after next May's Scottish Parliament election, Mr Murphy said: ''Yes.''

He conceded the election had been ''a dreadful night'', but said: ''Far worse than that we are waking up on a terrible morning for Scotland and for working-class people across the UK as David Cameron prepares to form another government.

''The friends and colleagues that were defeated last night had been faithful servants to our party and forceful advocates for their constituents.

''But this isn't about them and it isn't about us. This isn't about individual careers, because, while we have lost seats, the thing that hurts most is the loss of hope faced with another five years of a government totally lacking in compassion, and totally lacking in vision.''