THE secretary of Anas Sarwar’s local Labour branch has quit after raising concerns about an influx of new members signing up to vote in the Scottish leadership contest.

In the latest twist in one of the messiest political brawls in years, John Cork resigned just hours after it was revealed he had asked Scottish Labour HQ to probe apparent irregularities at Glasgow Southside Constituency Labour party .

The Sunday Herald reported Mr Cork, a supporter of Mr Sarwar’s left-wing rival Richard Leonard, raised concerns last week after hundreds of new members joined the CLP.

He claimed some new recruits had the same mobile number but different addresses, and several had the same business email address.

Separately, a Labour source told the Herald that staff at the Sarwar family’s cash and carry business had been urged to join up, and to encourage friends and family to do likewise.

A source close to the Sarwar campaign said some employees from United Wholesale (Scotland) had been “enthused to sign up”, but it was not suspicious.

Another source said Mr Cork had admitted raising the complaint without the authority of the CLP executive, and had been naive about the publicity it would would attract.

In recent days, the issue of new members has dominated the leadership race.

Supporters of Mr Leonard suggested there had been unusual clusters of new members, with common email addresses opening up the online ballot to potential abuse.

One of Mr Sarwar’s allies, Edinburgh South MP Ian Murray, then alleged a recruitment drive by the Unite union could have“rigged” the contest in favour of Mr Leonard.

A spokesman for Mr Sarwar: “It’s incredibly encouraging that people across Scotland have joined the Labour Party. It is deeply disappointing if anyone in the party is now launching a smear campaign against new members.”