A vote to decide whether Tower Hamlets Mayor John Biggs is re-nominated as Labour’s preferred candidate for the role has been thrown into controversy amidst allegations of ballot rigging.

Three local party members have asked Iain McNicol, Labour’s general secretary, to suspend an internal voting process aimed at deciding whether Biggs must compete in an open selection battle or be the only candidate for the next mayoral election in 2018.

Biggs won the mayoral election in 2015 after the initial result was declared void by an Election Court judge. Then mayor, Lutfar Rahman, was found guilty of corrupt and illegal practices after four Tower Hamlets residents brought a case against him last year.

The appeal to McNicol makes allegations about the conduct of the vote-counting process, after the Tower Hamlets Labour Party Women’s Forum ballot was cancelled. In a dispute over the number of votes cast, organisers claimed that 80 ballots were cast despite only 67 members registering on the night, earlier this month.

The Forum is one of 41 branches or affiliates of the local party that are being asked to vote on the selection procedure for the party’s next Mayoral candidate.

The Forum organisers, two of them vote counters, said it was either an administrative error during the registration process or more ballots had purposely been put in during the vote.

Catherine Overton, a 34-year-old lawyer and one of the organisers on the night, said: ‘There are two possibilities. One is that ballot papers were stolen and therefore an excessive number of votes cast. It seems to me likely that in fact it was the signing-in process that was defective and that people came in who we didn’t manage to record.’’

According to the aggrieved members, each woman had to undergo an exhaustive three-stage signing-in procedure before the release of the ballots.

Apsana Begum, a 26-year-old education worker and one of the co-authors of the letter of complaint, said: “I’ve been involved at elections at a local level, and sometimes ballots have had to be re-counted two or three times. Sometimes it’s been two or three votes out but it’s never been as big as thirteen.”

The Forum vote was crucial because Biggs currently has 20 out of a possible 41 wards and affiliates, needing one more to be selected unopposed as Labour’s mayoral candidate for 2018.

The members have received no reply from the Labour Party HQ as to whether the ballot will be investigated.