A top adviser to Rachel Reeves has been embroiled in a criminal investigation into vote-rigging.

Pearleen Sangha served as Labour’s London regional director when an MP candidate selection process was plunged into chaos in Croydon East.

The campaign to select a Labour candidate in the newly-made seat was ultimately suspended in suspicious circumstances.

Contact details for members across the South London constituency appeared to have been changed to be wrong systematically.

Phone numbers had been changed by a single digit and fake email addresses had been logged.

The change meant that some candidates were unable to reach key voters.

Labour later admitted email addresses, phone numbers and postal addresses had been altered without permission, sparking allegations that the selection process had been tampered with to benefit a particular candidate.

The Metropolitan Police has now passed a file to the Crown Prosecution Service, The Telegraph has reported.

There is no suggestion Ms Sangha is personally being investigated by Scotland Yard.

However, Ms Sangha had served as Labour’s regional director in London during the selection process.

Regional directors also play a direct role in the selection timings, hand-pick two people to help run the race and decide who can attend hustings.

Ms Sangha, who is a close ally of No10 chief of staff Morgan McSweeney, was brought into the Treasury as the Chancellor’s business engagement lead, a civil service position rather than a political appointee.

A CPS spokesman said: “We have received a file of evidence from the Metropolitan Police Service in relation to the Labour Party selection process for a candidate to represent the Croydon East constituency.”

A Met spokesman added: “We have received allegations of computer misuse in relation to an internal selection process for a political party in Croydon during October and November 2023.

“The Met’s cybercrime team are investigating and inquiries are on-going.”

A Treasury spokesman also said: “This is a civil service role, and all the correct rules and processes were followed when making this appointment.”