Voting for the Alba Party is in Scotland’s “national interest”, Alex Salmond has said.

In an address on Tuesday, Mr Salmond launched the Alba Party’s campaign for the Scottish elections in May, where he repeatedly pushed for a supermajority of MSPs to be elected in support of independence, but he failed to say the number he believed to be the threshold for a supermajority.

The former first minister also outlined his party’s view on how independence could be achieved if most MSPs elected were in support of separation.

Within the first week of the new parliament, Mr Salmond said, the Scottish Parliament should instruct the Scottish Government to start negotiations with the UK Government, creating a “standing independence convention” formed of elected representatives.

Their purpose would be to “give support and substance to the Scottish Government’s independence negotiating position”.

As a result of the negotiations, a referendum could be called, while another style of plebiscite, legal action, “international and diplomatic initiatives” and “peaceful and popular demonstration” were also options that could be explored, Mr Salmond said.

The former first minister urged his supporters to vote for his party on the regional list, while supporting the SNP in constituencies.

“I’ll be voting SNP in my first constituency vote for that reason and I know that tens of thousands of SNP supporters are going to vote for Alba on the list for exactly the same reason,” he said.

“Because it is in the Scottish national interest to do so.

“In that unity and common purpose lies our strength and our greatest opportunity to deliver independence.

“That approach can deliver a shared parliamentary purpose in Holyrood which changes the context of the debate and which tilts the balance of power in Scotland’s favour.

“It is the only way to guarantee that Scotland cannot again be sidelined and to ensure that democratic expression will prevail.”

Alex Salmond giving a speech
The former first minister will be standing on the Alba Party’s North East regional list (Andrew Milligan/PA)

Mr Salmond’s party’s success depends on electing what he calls a supermajority of independence-supporting MSPs who would ensure that the UK Government has to come to the table – but the Alba leader has so far not been able to say how many elected members would constitute such a majority.

In the Scotland Act 2016, a supermajority is described as two thirds of all 129 MSPs, meaning more than 86 would be needed for the Alba Party to reach its goal.

A Panelbase poll done for The Sunday Times this weekend suggested there could be up to 79 independence supporting MSPs elected in May.

However, Mr Salmond said: “That is not the definition of supermajority that we are using.”

He added: “If there were 70 MSPs supporting independence that would be a majority and I would expect to see that majority moving forward with an independence platform.

“If there were 80 MSPs supporting independence, as the polls at the weekend indicated, then we’d be well on our way to a supermajority.

“If there were 90 MSPs, which I think is well within our reach for the independence supporting parties, then that would be a bigger supermajority.

“The point we’re making in the campaign is the stronger the supermajority of MSPs are supporting independence in the Scottish Parliament, the more the balance of power will be tilted in Scotland’s favour.”

Scottish Labour deputy leader Jackie Baillie described Mr Salmond’s push to launch negotiations within the first week of the new parliament as “extreme”.

“For Alex Salmond to plan independence negotiations in the first week is an insult to all those jobs and livelihoods that are still at risk,” she said.

“Nicola Sturgeon cannot endorse this extreme approach to the constitution and needs to be clear that she will not bulldoze this through the parliament with an ugly allegiance with Salmond’s Alba Party.

“Scotland deserves better – and that is why Scottish Labour will devote its energy to delivering a national recovery plan so we can build a fairer and stronger Scotland together.”