“Major failings” by police led allowed electoral fraud Lutfur Rahman to remain mayor as evidence was missed, an investigation concluded today.

The disgraced Tower Hamlets mayor was banned from office in 2015 after Election Commissioner Richard Mawrey found Rahman guilty of electoral fraud relating to his 2014 mayoral campaign.

Today the London Assembly’s Police and Crime Committee called for an inquiry after publishing its findings as part of an investigation into the difficulties of tackling election fraud, revealing a bundle of 27 files of evidence weren’t reviewed by the Met in what committee chairman Steve O’Connell AM said was a shocking failure.

“During our investigation, we, as a committee, have been shocked to uncover major failings by the Metropolitan Police in its ability to investigate allegations of electoral fraud and malpractice,” he said. “Missed files of evidence; missed opportunities to gather witness statements; witnesses who were prepared to give evidence in the Election Court but were unwilling to do so in criminal proceedings – this is not what we expect from a supposedly world-leading police force.

“We urge the Deputy Mayor [for policing and crime] to use her powers to press for Her Majesty’s Inspectorate of Constabulary (HMIC) to take the matter further, with the aim that eventually we can assure Londoners – and particularly residents in Tower Hamlets – that justice has been done.”

The investigation said police failed to meet “highest possible standards” and concluded a more robust investigation could have secured a criminal prosecution, with the committee requesting a full investigation into the faillings.

Labour mayor John Biggs, who replaced Rahman’s Tower Hamlets First regime in 2015, said his banned predecessor paying £250,000 in costs was not sufficient.

“Despite a High Court judge finding Lutfur Rahman and his colleagues guilty on multiple counts of corruption and electoral fraud, there is deep frustration that the process stopped without criminal charges,” he said. “On the basis of the evidence in the election court there were many leads to follow.

“Many people in Tower Hamlets are understandably mystified why those who tried so hard to steal the 2014 election have yet to be fully held to account. I welcome the Police and Crime Committee’s call for the HMIC to be called in to see what lessons can be learnt from this sorry saga.

“Thankfully electoral fraud is rare but where it does happen we need confidence that the police have the skills and motivation to thoroughly investigate and bring those responsible to justice.”

A police spokeswoman said the Met attended the Police and Crime Committee on February 9, where it was revealed the Crown Prosecution Service (CPS) had not referred the 27 files for investigation.

“The CPS and the MPS have agreed to undertake a further joint assessment of the files to see whether they contain anything that changes the advice previously provided by the CPS, changes the decisions previously made by the MPS, or requires further investigation by the MPS,” she said.