THE prospect of a second independence referendum being held within the next three years has come closer after two influential SNP politicians who suggested postponing the vote until after 2021 have shifted their views.

Tommy Sheppard and Pete Wishart both sparked widespread debate when they separately made cases for putting off a new plebiscite until after the next Holyrood election and instead argued that that ballot should be used to win a fresh mandate.

But both MPs have now signalled changes in their thinking which they attributed to the political landscape shifting on Brexit.

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Sheppard said views he expressed in August about holding back on a referendum until after 2021 should now be regarded as the “default” position.

Delivering the Thomas Muir lecture, the Edinburgh East MP said: “Given the choice between getting a new, clear and unconditional mandate in 2021 or trying to resuscitate a heavily nuanced mandate linked intrinsically to Brexit, I know I would opt for the former.

“I know also that this scares some in the Yes movement, who fear that pro-independence parties may lose a majority in the 2021 parliament and the chance of a further referendum may disappear.

“To them I say: have confidence in your conviction. There is no reason why we cannot take support for independence to far greater levels than hitherto in the next four years.

“Besides, there is no shortcut for this. If there are not the numbers to elect an independence- supporting Scottish Government, then there ain’t the numbers to win a referendum in any event.’’

But last week Sheppard told the audience at a debate in Westminster Hall that if Theresa May fails to win the Scottish Parliament’s support for the EU Withdrawal Bill but presses on regardless, a second referendum was essential.

Last night Sheppard confirmed to The National a second referendum might be needed earlier than he had thought. He said: “The timescale of a second referendum will depend on how catastrophic things are. If things take a nosedive, we might want to do it quite quickly.”

He added: “2021 should be regarded as a default, if you like; regardless of what happens we should be planning for a fresh, unconditional mandate in 2021, that isn’t related to Brexit or anything else, that simply says it’s been nearly a decade, the world has moved on, things have changed. But between now and 2021 I wouldn’t discount the fact there may be a need to execute the existing mandate.”

Pete Wishart also said circumstances had changed since he set out in an article in The National in September favouring a post-2021 vote.

He said his position then was based upon there being a two-year Brexit transitional period from March 2019. Two months ago such a transition seemed likely, but was currently less so, he added.

“I said in my piece that given transitional arrangements, if they were to come into play, and would be in place, we would have to seek a renewed mandate in 2021.

“But my view has always been that when people start to feel the experience and impact of Brexit that is the optimum time, and that might be sooner than we anticipate given there is every real possibility that talks collapse, people see how perilous Brexit is, and by then the lifeboat of independence referendum is an option we should deploy.”

He added: “For me the optimum time has always been when we start to experience the consequences of Brexit, and that may be sooner than later if we are told there is no deal.”

Sheppard added it was possible the Scottish and UK governments could reach a deal on the EU Withdrawal Bill allowing the devolution settlement to be protected, and for Scotland to remain in the single market.

He added such an offer would be consistent with Scottish Government proposals almost a year ago, and would not see a referendum happen.

Wishart called for new arguments to be made for independence, in particular about what sort of relationship an independent Scotland would have with Europe and the EU.

After the snap General Election, in which the SNP lost 21 MPs, Nicola Sturgeon postponed plans to introduce a referendum Bill. She told MSPs she would “reset” her timetable after initially planning a new vote between the autumn of 2018 and spring of 2019.

Speaking on Tuesday after talks with May in Downing Street, she underlined her government’s mandate during the current Scottish Parliament, though added “no decisions would be made on timing until the terms of Brexit became clear”.

A Scottish Greens’ spokesman said: “The people of Scotland face being denied the right to make their own choice until after we leave the EU. In fact, the people of Scotland will be the only ones in Europe not to have their say on Brexit under the current timeline.”