A new pressure group created to promote Jeremy Corbyn’s left-wing political agenda will be launched in Edinburgh this week.

Momentum, described as a “grassroots network”, will be unveiled locally on Wednesday as a first step towards a national launch north of the border.

However, senior party sources fear the organisation could be a twenty-first century version of Militant, which tried to infiltrate Labour in the 1980s.

Corbyn won the leadership contest comfortably after winning support from party members, trade unionists and registered supporters.

But despite his victory, an overwhelming majority of the parliamentary Labour party remains sceptical of his ability to win a general election.

Scottish Labour also has a moderate leader in Kezia Dugdale, who is not naturally sympathetic to the Corbyn agenda.

Momentum was formed recently at a UK level as a successor body to the Corbyn leadership campaign, which attracted the backing of hundreds of thousands of people.

It describes itself as “a network of people and organisations that will continue the energy and enthusiasm of Jeremy's campaign”.

Momentum will organise events, rallies and policy consultations and attempt to forge links with campaigners outside Labour.

Left-wing Labour activists will launch a local branch of Momentum in Edinburgh at a venue in the Grassmarket this week.

One figure involved in group said Momentum supported the “aims and values” of Corbyn and added that they would reach out to non party members.

Vince Mills, the chair of the Campaign for Socialism in Scotland, told the Sunday Herald that Wednesday’s local launch would lead to a national organisation being unveiled in the next few weeks.

He said he hoped Corbyn or shadow chancellor John McDonnell would appear at the national Scottish launch.

However, senior party sources are worried that Momentum and the wider Labour left will seek to influence the party’s List ranking selections for the next Holyrood election.

With Labour predicted to get wiped out in constituency seats, the party is expected to return around 25 MSPs on the eight regional Lists.

The insiders believe the party’s left-wing is planning to put forward a pro-Corbyn candidate on each List.

Tom Harris, a former Labour MP in Glasgow who helped expel Militant members in the late 1980s, said:

“The question is: why do we need an organisation like Momentum? We already have the Labour party. I just don’t know what they think their role is.

“Momentum say they don’t want infiltration by the Socialist Workers Party, but what about the Greens and Tommy Sheridan’s party? Labour activists have to be very careful when it comes to the motivations of any of these organisations. The reason we managed to get rid of Militant is the National Executive committee recognised it was a separate party.”

Scottish Conservative chief whip John Lamont said: "This group, whilst seeking to promote Jeremy Corbyn's career, will only further undermine the Labour Party in Scotland.

"With Labour out of the picture, the only serious pro-union party to vote for in next year's Holyrood elections is the Scottish Conservatives."