LONG-SERVING SNP politician Alex Neil also called for a complete re-write of the economic case for independence.

The MSP for Airdrie and Shotts, who has been a serving Scottish politician since 1999, said his party should contest the Holyrood 2021 elections on a “clear, unequivocal commitment” to hold a referendum on the constitution in the next parliamentary lifetime.

It comes after the 69-year-old announced yesterday that he would be standing down at the next elections.

He urged his party to agree a joint mandate with pro-independence party the Scottish Greens to prevent their promises on a referendum being challenged, adding that the promise should be the “centrepiece” of the SNP’s campaign for 2021.

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The MSP who voted to leave the EU in the Brexit referendum has also issued a warning to Prime Minister Boris Johnson that if he continues to deny a second referendum in Scotland despite growing support for independence, the Scottish Conservatives would be “wiped out.”

Mr Neil said: “If the Scottish people elect a pro-independence majority to the Scottish Parliament with a clear democratic mandate to hold an independence referendum, Boris Johnson should not dare to stand in the way of Scottish democracy.”

Mr Neil predicted, that if “the UK denies the Scottish people their democratic right to determine our own future, then Britain’s international reputation as a modern liberal democracy would be in tatters” adding “It would also lead to the electoral wipe-out of the Tory Party in Scotland.”

In a statement he said he was “optimistic about Scotland’s long-term future” and described unionists as “weak and leaderless”.Boris Johnson and his Tory Government represent values which are alien to many people in Scotland, driving more and more of them towards independence.

“But victory for the independence movement is not yet in the bag, there is a lot more work to do to achieve our goal.”

The MSP said there had to be a second referendum “to make progress” and said that the SNP must put a second referendum during the next parliamentary lifetime as the “centrepiece” of its campaign.

He continued: “ To underline the strength and clarity of the mandate, the SNP should agree the wording of that commitment with the wider independence movement and in particular invite the Scottish Green Party to agree an identical wording for their manifesto promise of a referendum. That way the legitimacy of the pro-independence parties’ joint mandate cannot be challenged.

“If the Scottish people elect a pro-independence majority to the Scottish Parliament with a clear democratic mandate to hold an independence referendum, I do not believe that Boris Johnson would dare stand in the way of Scottish democracy.”

The economic case for Scottish independence, he said, must be “ completely re-written” to take into account the challenges caused by the Covid-19 pandemic.

He continued: “The case for independence needs to be updated as the world has moved on since 2014.

“It is difficult to see how we can re-build the Scottish economy without the tools available to independent nations, including a currency and central bank.

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“The SNP also has to re-visit its policy for an independent Scotland to join the EU, which would lead to customs barriers between an independent Scotland and the rest of the UK.

“It would make much more sense for an independent Scotland to join EFTA, which would secure access to European markets without the downsides of EU membership.”

Mr Neil has been an MSP since the establishment of the Scottish Parliament and held positions in cabinet under Nicola Sturgeon and Alex Salmond.

.He has held four ministerial posts as Minister for Housing, Cabinet Secretary for Infrastructure, Cabinet Secretary for Health and Cabinet Secretary for Social Justice.

After leaving Holyrood next year, he intends to continue his business interests and has vowed to continue to campaign for Scottish independence.