BRITISH identity must be “tackled and reviewed” if nationalists want to win a second independence referendum, a senior SNP MP has said.

Pete Wishart, the party’s longest-serving representative in Westminster, has warned against rushing into a second vote until the “optimum conditions are in place for success”.

He said Yes supporters must listen to and understand “persuadable unionists” in order to win them over, adding: “To win we are going to have to be creative.

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“Things like the cultural connections and attachments that are valued across these isles and even things like British identity are going to have to be tackled and reviewed.”

He said the SNP needed to take stock after losing a third of its MPs in last year’s general election, while polls continued to show a majority of Scots oppose independence.

Currency, pensions and “perceived deficits” all have to be addressed, he argued, as well as SNP voters who backed leaving the EU.

It comes as the debate over when to hold a second referendum continues to be the focus of the SNP's deputy leadership contest, with candidate Chris McEleny backing a new vote within the next 18 months.

In a blog post, Mr Wishart said First Minister Nicola Sturgeon’s decision to fire the starting gun on a second referendum last year had dominated the general election – during which the SNP lost half a million votes.

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He added: “Many have said that simply holding a new referendum will somehow secure a majority and just by initiating a renewed contest we will secure a victory.

“This ignores just how hard it is going to be to secure a majority. That last five per cent we need to win over in a renewed referendum will be the hardest five per cent we have ever had to convert.”

Mr Wishart, who chairs Westminster’s Scottish Affairs Committee, advocated “hitting the sweet spot when Brexit impacts and people actively want out of an isolated, desolated UK”.

He said the optimum conditions for another referendum meant “seeing support for the SNP returning to the levels we achieved around the last referendum in electoral contests”.

The Perth and North Perthshire MP added: “It means evidence. If securing our independence was easy we would already be an independent country.

“This is going to be hard, hard work and no amount of just wishing it can be easily achieved just because we want it is going to get us there.

“We owe it to future generations of Scots to win this and rescue our nation from a disastrous Brexit and a UK determined to erode out national Parliament. We simply have to have a nation of our own run by those of us who live and work here.”

He insisted “losing again is simply not an option”.

It comes as Mr Wishart lashed out at the UK Government's “unsustainable and untenable” Brexit position, suggesting it is “all over the place”.

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He made the comments on the BBC’s Sunday Politics Scotland, during which Scottish Conservative MP Stephen Kerr appeared to suggest the UK Government wanted “a” customs union with the EU.

Mr Kerr, who represents Stirling, signed a letter in February insisting the UK must gain full "regulatory autonomy" after Brexit, but yesterday appeared to support "some kind of customs agreement".

Labour have called for a new customs union after Brexit, but Prime Minister Theresa May has ruled it out in the past. However, there are now suggestions her position may be softening amid parliamentary pressure.

Mr Kerr said: “The Prime Minister has been absolutely clear, and repeatedly so, in each of the major speeches she’s given, and repeatedly at the despatch box in the House of Commons.

“We are leaving the customs union – however, that does not mean that we… We absolutely do need to negotiate a trade agreement, a free trade agreement with the EU, and that should involve tariff-free trade. And so there needs to be some kind of customs agreement.”

Pressed on whether he thought Britain needed a customs union with the EU, he said: “That is the Government’s position, and that’s my position as an MP.”

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However, he later softened the statement by insisting the UK Government seeks to negotiate a “deep and meaningful free trade deal with the EU”.

Referring to Mr Wishart's blog, a Scottish Tory spokeswoman said: "The Scottish people have already been subjected to a lengthy and divisive referendum debate and they were persuaded of the benefits of the Union.

"The SNP must now focus on the day job and give up this constitutional obsession."