The Metropolitan Police has attempted to clarify its view of evidence presented to the Election Court trial that brought down former mayor Lutfur Rahman after confusion left campaigners furious.

On March 16, a year after the court issued a damning verdict on Mr Rahman, a special inquiry team at Scotland Yard concluded no action would be taken against other culprits mentioned in evidence.

The police said at the time: “The rules regarding admissibility of evidence and liability were different to those applied for any criminal prosecution.”

Campaigners were frustrated by the result and accused the police of misunderstanding the standing of the court. While the trial was held in a civil court, Judge Richard Mawrey had made clear he was operating to the same standards of proof as a criminal court.

Background Fury as Scotland Yard closes book on Tower Hamlets election fraud claims

Campaigners argued this gave Scotland Yard the legal muscle it required to pursue a root and branch probe of corruption in Tower Hamlets .

Asked by The Wharf to clear up the apparent misunderstanding, a police spokesman said: “The Election Commissioner made his findings using the criminal standard of proof, but in doing so he used evidence that would not have been available in criminal proceedings.

“The MPS does not seek to disagree with the Election Commissioner’s reference to the standard of proof he applied in the High Court proceedings. This however has no impact on the CPS decision that there was insufficient evidence to proceed with a criminal prosecution.”

Disgraced: Lutfur Rahman trying to hide under a fishing hat as he arrives at the High Court during the election case

The answer has not satisfied campaigners. Andy Erlam, one of the petitioners who brought the case, said: “The offences were proved to the criminal standard – ‘beyond reasonable doubt’. I don’t think the police team were ever looking for the evidence. I believe there has been a massive police cover-up. The question is: why?

“The Met Commissioner should now resign.”

Cllr Peter Golds, an Isle of Dogs Conservative councillor and long-time champion of transparency in the Town Hall, referenced similar trials elsewhere in the country.

He said: “In the judgments following petitions in Birmingham, Slough and Woking, the local police forces followed up using the evidence trail identified in the election courts and secured convictions.

Background Lutfur Rahman supporters hail Scotland Yard decision

“I have read every word of the Slough election petition judgment and the evidence is eerily similar to Tower Hamlets, as was that in Woking.

“Casting a false vote is a corrupt practice and the proof was glaring. The Met are simply frightened.”

Mr Erlam said the matter would not rest. He said: “My colleagues [community activists] Angela Moffat and Cathy Holmes are already talking to lawyers, as they decided last week to commence a private prosecution.

“If the CPS takes over that prosecution and closes it down – as it has the power to do – we will know that the scandal goes even wider. The truth will out.”

What the judge said about policing Tower Hamlets

“Policing Tower Hamlets under its [Lutfur Rahman’s] political régime is not an easy task.

“Many in the Police feel that the imputation of ‘institutional racism’ made by the Macpherson Enquiry, albeit 16 years ago, still dogs the force and they are conscious that, in Mr Rahman, whose personal control of the borough is tight, they are dealing with a man whose hair-trigger reaction is to accuse anyone who disagrees with him of racism and/or Islamophobia.

“In the circumstances it would be unreasonable to expect of the police anything other than an approach of considerable caution."

Judge Richard Mawrey QC

Explainer: Standard of proof

Standard of proof is the measurement of the quality of evidence that needs to be put before the court by the parties who have to carry the burden of proof to win a case.

In a civil case, the standard of proof is the “balance of probability” – that is, the case is more likely than not to be true.

It is a tougher test in criminal cases and its most famous encapsulation is that the jury must be satisfied “beyond reasonable doubt”. In other words, they must be sure their verdict is right.

This difference is why, for example, OJ Simpson was cleared of murder in a criminal case but found liable in a civil case, where the burden of proof was lower.

However, there are civil cases where a criminal standard of proof is required.

In the High Court of Justice Queen’s Bench Division in the matter of the Tower Hamlets election Judge Richard Mawrey QC wrote: “There was no controversy at the hearing about the standard of proof the court must apply to the charges of corrupt and illegal practices.

“It is settled law that the court must apply the criminal standard of proof, namely proof beyond reasonable doubt.”