THE SNP should start preparing its own plan for a second independence referendum if Boris Johnson doesn’t grant one by Easter, a senior member of the party has said.

The suggestion adds to the pressure on Nicola Sturgeon to change tactics in the face of the Prime Minister’s blunt refusal to give her a legally watertight Indyref2 this year.

It could now become a major issue at the SNP’s October conference.

The idea has come from Chris McEleny, the leader of the SNP group on Inverclyde Council, who has become a leading advocate of a ‘Plan B’ on independence.

A former candidate for the party’s deputy leadership, he said it was "no longer sustainable to kick any discussion on a Plan B into the long grass".

In the wake of the SNP’s general election gains in December, Ms Sturgeon asked the PM for a transfer of power to Holyrood to hold Indyref2 under a so-called Section 30 order.

Mr Johnson refused, saying another vote would add to the political “stagnation” in Scotland.

Although Ms Sturgeon recently insisted Indyref2 was still possible this year, she has yet to identify a tangible mechanism other than Mr Johnson unexpectedly changing his mind.

She has not ruled out a consultative referendum in defiance of Westminster, but has also warned it could send the Yes movement backwards.

With time running out before a referendum becomes technically impossible this year, Mr McEleny said if Mr Johnson did not grant a Section 30 order by Easter, the SNP should discuss “alternative strategies” with an eye to the 2021 Holyrood election.

He said that by Easter it would be plain there was “no realistic prospect of a referendum happening in 2020” and the party would need to change tack.

He said: “The 2021 election cannot be fought just to gain the same mandate that’s been ignored repeatedly without the SNP having any Plan B to ensure the Prime Minister has a political price to pay.”

He said the party should agree in October to state in its manifesto for 2021 that the election of a majority of pro-independence MSPs would be a mandate to hold a “consultative referendum” without Westminster’s agreement.

If that referendum then delivered a Yes, it would be a mandate for the Scottish Government to open independence negotiations with Westminster.

SNP MPs Joanna Cherry QC, Kenny MacAskill and Angus MacNeil also back a consultative referendum, but to trigger a court challenge by the UK Government that would clarify whether Holyrood has the power to hold Indyref2 under its existing powers.

Mr McEleny said: “If the UK Government continues to refuse us our right to exercise democracy via an agreed referendum then we should rely on our own sovereign and democratic parliament to deliver that. If the section 30 demand has not been acceded to by Easter then it is no longer sustainable to kick any discussion on a Plan B into the long grass.

“It is clear that support is growing for countering the anti democratic position of Boris Johnson and it’s getting close to the end of the road for repeatedly saying we might have a referendum simply if we just keep asking nicely.

“Next year’s Holyrood election– should feature an SNP manifesto commitment that should Boris continue to refuse a section 30 order then, by a majority of pro-independence Scottish seats the people of Scotland mandate the Scottish Government to hold a consultative referendum on Scottish independence, with a resulting Yes vote being a mandate for our government to then open independence negotiations with Westminster.

"Faced with that clearly stated proposition Boris Johnson may run off scared to the courts, he could well even reconsider his rhetoric on a Scottish referendum.

"If he does not, then so be it."

Mr McEleny and Mr MacNeil previously tried to get a Plan B adopted at SNP conference but failed to get the idea discussed on the floor of the gathering in Aberdeen last October.

An SNP spokeswoman said: "The SNP Government has a cast-iron democratic mandate to hold an independence referendum - that is not a matter of opinion, it is a matter of fact.

"Boris Johnson's anti-democratic actions are only helping to make the case for independence - and the more that the Tories try to block the right of the people of Scotland to choose their own future, the more support for a referendum, and for independence, will continue to rise."