SCOTTISH Labour is bracing itself for a series of “faction fights” between supporters of Richard Leonard and defeated leadership contender Anas Sarwar over the selection of Westminster candidates.

Thousands of new members recruited by Sarwar’s team during the recent leadership campaign are expected to be pivotal in determining who will get selected.

Membership figures in Glasgow and Lanarkshire have increased substantially, with the numbers in Glasgow Southside – Sarwar’s local party – rising by over 100 per cent to around 1400.

A senior party source said the “scene is now set” for infighting between pro-Sarwar members and the left-wing Campaign for Socialism (CFS) group, which is twinned in Scotland with the pro-Corbyn Momentum organisation.

The insider predicted that the new members could have a kingmaker role in the imminent contests and block allies of UK leader Jeremy Corbyn from getting picked.

Scottish Labour’s membership has doubled since the independence referendum – from around 12,500 to nearly 26,000 – a surge attributed to Corbyn and various internal elections north and south of the border.

Around 2,500 members were added during the last Scottish leadership contest, which pitted left-wing Leonard against Sarwar, a centrist.

Leonard succeeded in signing up trade unionists as "affiliated supporters" – a separate route into the party – but the vast majority of the 2,500 were recruited on the Sarwar side.

It is understood the 100 per cent-plus surge in Glasgow Southside occurred between late 2016 and the Scottish leadership contest ending last year.

Until recently, Edinburgh Southern was the largest local party in Scotland, with the units in Glasgow Kelvin and Edinburgh Central also having a sizeable membership base.

However, Glasgow Southside is believed to be way ahead of Edinburgh Southern and is easily the biggest constituency party in the country. Other local parties in Glasgow have also witnessed big increases.

The focus is now on the impact the new recruits could have on the selection of parliamentary candidates for Westminster. Labour has identified 20 target seats in Scotland.

At the 2017 general election, left-winger Matt Kerr lost to Nationalist Chris Stephens by 60 votes in Glasgow South West (GSW) and he was expected to be a shoo-in for the selection.

Some of the new members in Glasgow Southside are likely to be eligible to vote in the GSW selection and the left is expecting a Sarwar ally to challenge Kerr.

It is understood that CFS – which doubles up with Momentum – are in the process of considering which left-wingers they want to support during the selections.

One insider said the selections would be a series of “proxy battles” between the supporters of Sarwar and Leonard:

“The scene is now set for faction fights. Anas may have lost, but the new members who were brought into the party have a lot of power.”

The leadership contest between the two MSPs, which Leonard won decisively, was marred by a number of spats on sign-up strategies.

Sarwar allies complained about the way the trade union Unite contacted potential affiliated supporters, while Leonard backers expressed concern about some of strategies adopted by the rival camp.

John Cork, who was Secretary of the Glasgow Southside party during the contest, raised concerns about some new members sharing a mobile phone number while being listed at different properties.

Stephen Low, a pro-Leonard member of the party’s governing executive, also raised the alarm during the contest about recruitment in the same local party.

In an email to Scottish Labour general secretary Brian Roy, which was leaked to the Herald, Low wrote: “Frankly I don’t think the vast bulk of the people on this list should be issued ballot papers without the Party receiving written confirmation from each individual that they know they are a Labour Party member.”

A Scottish Labour spokesperson said: “Scottish Labour is looking forward to selecting candidates to set out our positive vision for transforming our country. We are focussed on getting rid of this shambolic and cruel Tory government and on the election of a Labour government which will work for the many not the few.”