THE renewal of Trident could lead to a second Scottish independence referendum, Alex Salmond has indicated, saying opposition to the nuclear deterrent was “in the SNP’s DNA”.

In an exclusive interview with The Herald to mark the anniversary of the 2014 referendum, the former First Minister said that renewing Trident - alone or in a combination with other issues - could result in a fresh poll, saying there were “now at least four material circumstances bubbling away at the present moment; they all explain the engine behind the SNP's post-referendum (success)”.

At the end of July, Mr Salmond said in a BBC interview that there were “three issues”, which were moving matters towards a second referendum on a timescale yet to be determined.

The first was the refusal to deliver on the Vow of more extensive powers for Holyrood, the second was the threat of Scotland being pulled out of the European Union against its will and the third was “austerity to the max”.

Following a House of Commons debate on allegations made by a Royal Navy whistleblower about the security of the missiles at the Faslane base, the ex-Nationalist leader said it would be a “fatal mistake” for the UK Government to proceed with the main-gate decision on a new fleet of nuclear submarines.

This is due early in 2016 and so will coincide with the Scottish parliamentary election campaign; a crunch vote on Trident renewal is expected at Westminster.

Asked directly at the time of the whistleblower debate, if renewing the deterrent could spark another referendum, Mr Salmond replied: “You would have to ask Nicola Sturgeon whether this counts as a change in material circumstances."

The MP for Gordon made clear he now regarded Trident renewal as a fourth trigger issue, referring to the Chancellor’s recent visit to Scotland to announce a £500 million investment in the deterrent programme, which the Treasury stressed would help maintain up to 7000 defence jobs.

Describing George Osborne as someone “who personifies ‘too clever by half’”, he claimed that the announced investment on Trident renewal was “clearly, down here, meant to trap Corbyn as a peacenik but in terms of the Scottish constitutional debate was a very foolish thing to do”.

Asked if Trident renewal could then be a trigger for a second referendum, Mr Salmond said: “These are four issues, any one of which and a combination of them most certainly, could provide a change in material circumstances, which both identifies what Nicola has been talking about and would belie my(once in a generation) forecast of the timescale for a constitutional referendum.”

He went on: “Lots of people are opposed to Trident; it’s in the SNP’s DNA. The idea George can flounce up and say I’m announcing it before the parliamentary vote. There are lots of people who say wait a minute; this is a decision that’s meant to take place (at Westminster), not one you flounce up and announce...”

Mr Salmond’s remarks follow last week’s Ipsos Mori poll, which put support for independence at 53 per cent and opposition at 44 per cent, but it also suggested there was not a public clamour for Trident renewal to trigger a second referendum; this proposition received only 41 per cent support.

Following that snapshot, Ms Sturgeon sought to dampen SNP supporters’ hopes of a quick re-run of last September’s poll, repeating the line that another referendum would be supported only if there were a “material change in circumstances”.

The dilemma for the FM, who will come under pressure to go sooner rather than later at next month’s SNP conference, will be how strong a commitment to a second poll she puts in her party’s 2016 Holyrood manifesto.

Mr Salmond contemptuously dismissed Mr Cameron’s assertion that there was, in fact, “no need” for a second referendum but, given Westminster retained authority over referendums, it was pointed out the Prime Minister could withhold legal authority.

“At the end of the day people will vote; they won’t hold that line. Party or parties, if they have a mandate, then they’ll have a referendum and Westminster will agree to it. Cameron? It’s just hot air.”

The party grandee, who firmly believes Scotland will achieve independence in his lifetime – he is 60 - was asked about some Nationalists’ fears that the political momentum might not be with them for long and that the iron for calling a second poll might not be so hot in 2020 or 2025?

“Or,” he replied, “it might be white hot. That's a matter of political judgement. That's why it's so wonderful we have somebody with such impeccable political judgement in charge of those things.”