The former Conservative MP Harvey Proctor has agreed a settlement with the Metropolitan police after being subject to false accusations of child abuse and murder, with reports putting the figure he is due to receive at £900,000.

Proctor, whose home was raided as part of the disastrous Operation Midland investigation after fictitious claims made by Carl Beech, is to receive £500,000 in compensation from the Met plus nearly £400,000 towards his legal costs, according to the Daily Mail.

When contacted by the Guardian about the payout on Thursday, a spokesperson for the Met confirmed that a settlement had been agreed but would not disclose the figure.

Mark Stephensof the law firm Howard Kennedy, which represented Proctor, said the £900,000 payment was the largest ever made to a complainant who had not gone to prison and was the first time the police had ever “bought off” a claim for negligence.

“Historically, the police cannot be sued for negligence but this payment recognises that that [immunity] may be up,” Stephens said. “They recognised that it’s not sustainable where they have been so heavily criticised by a judge.”

Proctor was engaged in an 18-month legal battle with the force.

Operation Midland, which was conducted by the Met in London from November 2014 to March 2016, investigated several high-profile people over accusations of child sexual abuse and homicide. Other raids were made on the homes of the D-day veteran Lord Bramall and the former home secretary Leon Brittan.

However, the 18-month operation turned out to be based on a series of lies told by Beech, then known as “Nick”. Beech had falsely claimed that he and other boys were raped and tortured in the 1970s and 80s by members of a VIP paedophile ring. Brittan died before learning he had been exonerated.

Proctor stated in a high court document that the accusations resulted in him losing his job and home, and caused a “major depressive illness”. A key part of the legal action concerned the senior detective Kenny McDonald’s public statement, made during the early stages of the investigation, that Beech’s allegations were “credible and true”.

Proctor said that “elementary research” by the police would have shown Beech’s allegations were false. Beech is now serving an 18-year prison sentence for 12 counts of perverting the course of justice and one count of fraud.

The Met was heavily criticised over Operation Midland in an independent review of the case by the former high court judge Sir Richard Henriques.

He reprimanded the force for believing Beech for too long, Det Supt McDonald for his “credible and true” statement, and officers for applying for search warrants with flawed information and for failing to close the investigation sooner.

Earlier this month, Proctor announced he had reported five former Met officers to Northumbria police in an effort to start a fresh inquiry into the investigation. They include allegations linked to applications for search warrants in Operation Midland and the “credible and true” statement. Northumbria police has referred the matter back to the Met.

A spokesman for Scotland Yard said the force was “assessing the complaint”.

The police watchdog, the Independent Office for Police Conduct, found no evidence of misconduct or criminality by the officers during Operation Midland.