The word historic is overused when it comes to elections and political events – but what we have witnessed in the past few days is properly deserving of that description. Whatever the future of Scottish and UK politics, the events of the early hours of Friday are a moment in time that will be studied and debated for decades to come.

The result of the general election in Scotland was more than just historic; it was era-defining and epoch-shaping in its scale and magnitude. The size of the swings the SNP achieved to topple seat after seat, sweeping away Labour and Lib Dem bastions was simply awesome.

Many of the swings eclipsed those in some of the SNP’s historic by-election triumphs of previous generations. The total number of votes the SNP gathered – well over 1.4m – was more individual ballots than had ever been cast for any political party in any previous election in Scotland.

It is clear that the tectonic plates of Scottish politics have shifted and shifted decisively.

The demise of Labour across Scotland has been a long time in the making and as such, Friday’s results were in one sense merely the culmination of a process that has seen communities across swaths of Scotland become more disillusioned with a party once seen as their natural home. For too long, many of those elected under the Labour banner have failed to properly represent the communities that have placed their trust in them.

The stunning results the SNP achieved in the 2011 Holyrood elections should have been the major wake-up call that Labour needed. But it assumed that a Westminster election would see a return to business as usual. And, crucially, Labour was fatally undermined by its alliance with the Tories in last year’s independence referendum campaign.

That was a toxic partnership for Labour, as indeed it was for the Lib Dems, with huge numbers of supporters of both parties switching their allegiance to the SNP last Thursday.

Scotland as a whole may not have voted Yes to independence last September, but there is no doubt that the bitter, negative and hectoring tone of the No campaign and its constituent unionist parties was deeply resented by very many Scots.

Friday’s election result is proof of that, suggesting as it does that huge numbers of people across Scotland are completely disillusioned with the rhetoric and policy platforms of all the establishment parties at Westminster.

I said before the election that being the largest party in England could not be the only test of legitimacy for a Westminster government and that greater legitimacy would always attach to building a majority from across the whole of the UK.

Clearly, David Cameron’s new majority Tory government, with only one MP out of 59 in Scotland, fails that test. There was already a democratic deficit in Scotland under the previous Tory-Lib Dem coalition, which had just a dozen seats north of the border. That democratic deficit has suddenly become much more pronounced.

That makes it all the more essential that the new Westminster government listens to the Scottish people. I made clear before the election that, regardless of how many SNP MPs were elected, it would not be a mandate for independence or for a further referendum, and I stand by that.

Any independence referendum would be a matter for a Holyrood election and would require the electorate to endorse a specific manifesto commitment.

For now, what is required is a relationship of mutual respect and cooperation between governments in Edinburgh and London.

Mr Cameron must recognise that the result in Scotland means it cannot be business as usual – his government must listen and cooperate: anything else would be to defy the democratic will of the people of Scotland.

There are huge issues and challenges ahead – not least the looming question of the UK and Scotland’s place in Europe. A key requirement of the prime minister’s in-out referendum should be a “double-lock” requiring the assent of all four UK home nations before any withdrawal from the EU, and that is a condition I reiterate today.

Scotland spoke and spoke decisively last Thursday, and the future of Scottish and UK politics will never be quite the same again.