DEMAND for a second independence referendum could increase if the Corbyn Effect does not take off in Scotland, a senior Scottish trade union source has said, writes Michael Settle from the TUC conference in Brighton.

The key insider told The Herald that the acid test for Jeremy Corbyn north of the border would come next May in the Holyrood elections. At present, given the SNP's dominance in the opinion polls, it is said that Scottish Labour HQ is working on the assumption that the party will lose all its constituency seats and will have to rely on representation at Holyrood from the regional list top-up seats.

Scottish left-wingers are hoping strongly that the Corbyn Effect will take off north of the border in a major way, particularly as the new Labour leader has made clear Scotland is a “top priority” for his leadership; he is due in Edinburgh this week.

The senior Scottish trade union source said: “Jeremy Corbyn has obviously, within the Labour Party at least, tapped into a desire for change and a different approach to the economy; an anti-austerity programme, a desire to move away from the welfare cuts and look at a more progressive approach to tackling the issues of poverty and inequality.

“His challenge will be to galvanise the public around that message of change and that demand for change. In some respects, the SNP have tapped into a similar mood in Scotland and benefited from that after the referendum in the General Election.”

He suggested the key test for the Labour leader in Scotland would be to see if he could win back disaffected Labour supporters in light of the SNP’s landslide election victory and its continuing dominance in the opinion polls at next May’s Holyrood elections. A failure to reconcile the SNP switchers back to Labour would present Kezia Dugdale, the Scottish Labour leader, and her colleagues with the “significant challenge of asserting an influence on Scottish politics”.

“If that (Corbyn Effect) doesn’t happen and Labour are not successful at the Scottish parliamentary elections, I suspect it will put Jeremy Corbyn under significant pressure and raise concerns that Labour are not a viable opposition to the Conservatives at Westminster and are unlikely to win the next General Election.

“That may increase the demand for further constitutional change in Scotland, including the possibility of an increased demand for another referendum on independence.”

The remarks from the senior Scottish trade unionist come after Alistair Darling, the former Labour Chancellor who led the Better Together campaign, warned that Labour must not lurch to the Left following Mr Corbyn’s overwhelming victory in the party’s leadership contest.

The former Edinburgh MP made clear that he could not see a "silver lining" to the left-winger’s triumph and urged Ms Dugdale to remain rooted in the political centre ground, saying Scottish Labour would pay a "heavy price" if it attempted to challenged the SNP from a platform far to the left of Nicola Sturgeon's party.

The source’s remarks also follow a warning to Mr Corbyn and his colleagues from Ms Sturgeon, who said: “If Labour cannot quickly demonstrate that they have a credible chance of winning the next UK General Election, many more people in Scotland are likely to conclude that independence is the only alternative to continued Tory Government.”

Some pro-Unionist sources have begun to air concerns that, given Labour was the main political force to campaign against Scottish independence last September, that if the Corbyn leadership led to deep divisions within the party and even to a political implosion, then this would leave the pro-UK forces in disarray, and could help encourage the First Minister to decide to go for a second referendum sooner rather than later.