Election 2015: I've known Nicola Sturgeon for 20 years and she'd never do deal with David Cameron

Britain's general election news over the last few days has been dominated by ill-informed talk of the SNP and its prospective bedfellows. For those of us north of the border, it was only a matter of time before the right-wing press exacted revenge on Scotland's First Minister, Nicola Sturgeon, following her assured performance in last week's televised debate between the main party leaders.

Sure enough, it was less than 48-hours before there surfaced a 'leak' of her private conversation with the French ambassador – or rather, a second-hand gloss by a UK civil servant who had not been present – in which the First Minister supposedly professed her preference for David Cameron as Prime Minister.

The next day Nicola penned an open letter in The Observer to put the record straight, denying the substance of the leak – as did the French ambassador. The First Minister went further and repeated the SNP's invitation to Labour leader Ed Miliband to form a progressive alliance against the Tories.

She wrote: "I repeat my challenge to Ed Miliband - if together our parties have the parliamentary numbers required after 7 May, and regardless of which is the biggest party, will he and Labour join with us in locking David Cameron out of Downing Street?"

To date, Miliband has not responded. But it is significant that the Labour leadership, while publicly rejecting a formal coalition with the SNP, nevertheless studiously refuses to rule out accepting support from the Scot Nats. Current polls put the SNP on course to win a majority of the Westminster seats in Scotland.

Faced with a meltdown in its Scottish heartland, it is no surprise Labour is keen to talk up the notion of Nicola Sturgeon favouring a Tory victory. Labour activists are playing up the resignation from the SNP of Mohammad Shoaib, a leading light in the Asians for Independence group last year, who now claims that SNP members in Nicola Sturgeon's own consistuency are "secretly backing Cameron".

No smoke without fire? Shoaib's credibility is in doubt as it is only a matter of months since he tried – and failed - to secure the SNP nomination to stand for Westminster in the Glasgow Central constituency. More like sour grapes, then.

Nevertheless, I can understand people in the rest of the UK feeling rather confused by these events. So let me clarify.

For starters, the SNP has recruited over 80,000 new members since the independence referendum last September. We've recruited another 3,000 in the past week alone. These new recruits are overwhelmingly anti-Tory. Many are ex-Labour supporters appalled by Jim Murphy's support for more austerity. It is beyond belief anyone could mistake this left-wing, anti-austerity movement for prospective Tory allies. Nor could any SNP leader do a deal with Cameron and survive.

I've known Nicola Sturgeon for over 20 years. Her position is clear: we will not enter into any form of support for another Tory government and we'd like to form a progressive alliance with Labour if, together, we can outvote the Tories.

The SNP offered just such a deal to Gordon Brown after the 2010 general election. A progressive alliance of Labour, the Scots and Welsh nationalists, and the Lib Dems could have locked David Cameron out of Downing Street. Unfortunately, Labour rejected the suggestion out of hand. I hope they are not so selfish this time.

An end to austerity

Our preference for a progressive alliance with Labour, the English Greens and Plaid Cymru is very clear in terms of our policies, which are manifestly to the left of Labour. We want an end to the austerity propounded by the Tory government and mimicked by Ed Balls, the Labour Shadow Chancellor. Both want to eliminate the current budget deficit entirely. The SNP wants to increase public spending gently, to grow the economy, while still bringing down national debt as a percentage of GDP. We believe governments have a social duty to their people, as well as an economic one.

The SNP group at Westminster are committed to securing the Home Rule (devo max) promised by the unionist parties during the referendum. We will vote against any attempt to privatise or franchise the English NHS, because we believe in public service, and because any reduction in spending on health in England will have negative consequences for Scotland. We would demand the end to plans to replace the present Trident nuclear deterrent, saving £100 billion.

Does any of this sound like a blueprint which would sit well with a Tory Chancellor? There is simply no way the Conservatives would facilitate the policies we want, and there is no we would countenance an alliance with them.

Nicola, Alex Salmond and the rest of the SNP leadership are in agreement on this. And, despite what Mohammad Shoaib says, 100,000 SNP members are in agreement as well. We are only contemplating a progressive alliance with Labour. Anything else would be a betrayal of Scotland.

George Kerevan is a former Associate Editor of the Scotsman newspaper and is the SNP candidate for East Lothian. He is an economist by training. He was in the Labour party for 16 years and a Labour councillor in Edinburgh for 12 years. He joined the SNP in 1996 after Tony Blair became Labour leader.

Follow George on Twitter @GeorgeKerevan.