Labour has ruled out entering into formal alliance with the SNP to oust Boris Johnson amid mounting speculation over the prospect of an early general election.

Andrew Gwynne, the party’s elections coordinator, said Labour had set its sights on No 10 and would rule as a minority government if it could not win a comprehensive victory in a snap poll.

In an interview with The Independent, Mr Gwynne said Labour offered an alternative to the “charlatan” prime minister, whose “bravado and bluster” was hiding the risks of a no-deal Brexit.

Westminster is braced for Jeremy Corbyn to bring a confidence vote against the new prime minister in September, as MPs gear up for a series of Commons battles to thwart a no-deal Brexit.

Downing Street has signalled Mr Johnson could call a general election around the 31 October Brexit deadline, if he is forced to go to the country by a no-confidence vote.

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Questions were raised over a possible SNP-Labour pact, after the shadow chancellor John McDonnell appeared to offer an olive branch to Nicola Sturgeon by saying his party would not block a second Scottish independence referendum.

Setting himself at odds with the Scottish Labour stance, Mr McDonnell refused to row back on his comments, triggering speculation he was laying ground for an alliance with the Scottish nationalists.

Asked if Labour would make a pact with the SNP, Mr Gwynne said: “No, I think that what we should say as we would govern as a Labour government.

“We would aim for a majority Labour government but the reality is that apart from two years where David Cameron managed to secure a very small majority, since 2010 all the governments have been formed in hung parliaments.

“We will aim to win a majority Labour government but if we don’t, we will govern in a minority.

“It will be down to every other political party to decide whether they want that radical agenda and a change of direction or if they want more of the same under the Tories.

“If the SNP want to prop up a Tory government under Boris Johnson, on their own heads be it. I don’t think Scotland will forgive them for that.”

Labour will aim its firepower at winning back seats from the Tories in Brexit-voting heartlands by tackling what it sees as the reasons behind the Leave vote, such as lack of investment in infrastructure and industry.

However, Mr Gwynne said it was relaxed about winning back seats from defectors such as Chuka Umunna, now a Liberal Democrat, and veteran MP Frank Field.

The shadow communities secretary said: “We have to reach out further into places like Scotland, and in the midlands and the north where there are a whole string of very marginal seats that we came close in 2017 and need to win in order to form a majority Labour government.”

He added: “A no-deal Brexit could be incredibly damaging to precisely those communities that feel that they’ve been left behind for the past 30 years.

“Actually the answer for those communities is to invest in jobs and skills and infrastructure, and in the jobs of the future, the green industrial revolution, the next industrial revolution. On all of those issues, the Labour Party is really coming up with the answers for the future.”

The comments come as Gordon Brown warns that growing nationalism is tearing the United Kingdom apart, with England, Scotland, Wales and Northern Ireland "devoid of a unifying purpose" that can hold them together amid an increasing likelihood of a no-deal Brexit.

Writing in The Observer, the former prime minister – who was born and raised in Scotland – says unionism "is sleepwalking into oblivion", adding: "We must rediscover the age-old virtues of empathy, solidarity across borders, reciprocity between nations and co-operation rather than conflict.

"These precious ideals – and a tolerant, inclusive and outward-looking Britishness – could not survive the divisiveness and chaos of a no-deal Brexit."

Meanwhile Mr Gwynne, who famously got into in a heated on-air tussle with Mr Johnson during the 2017 election campaign, said: “We’ve really got to show Boris Johnson as the charlatan that he is.

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“For all his bravado and bluster, it’s the communities that the Labour Party seeks to represent that will be damaged the most [by a no-deal Brexit].”

Labour can win at the polls as Mr Johnson is already discredited by his record in government, the frontbencher added.

However, a recent poll by YouGov gave the Tories a nine-point lead over Labour, with the resurgent Liberal Democrats close to challenging Mr Corbyn’s party for second place.

According to the survey over 5-6 August, the Conservatives were on 31 per cent, with Labour on 22 per cent, and Jo Swinson’s party on 21 per cent.