Julian Bennett, who joined the force in 1976, was cleared by a disciplinary panel of using the drug at home in late 2019.

However, he was found to have committed gross misconduct by failing to provide a urine sample for a drugs test on 21 July 2020.

Mr Bennett's former flatmate Sheila Gomes claimed he had used the substance daily before breakfast and leaving for work at New Scotland Yard, but the three-person panel rejected that allegation.

The panel also rejected an allegation that he had given an explanation for refusing a sample which he "knew to be untrue".

After Ms Gomes reported Mr Bennett in July 2020, he was called in and, in the presence of an assistant commissioner, was asked to provide a sample.

He offered to resign on the spot instead, and asked for a meeting with then-commissioner Dame Cressida Dick.

Mark Ley-Morgan KC, representing the Metropolitan Police, said it would have smacked of "organised corruption at the highest level" and compromised her integrity if Mr Bennett had been allowed to resign on the spot.

Mr Bennett said he had been taking CBD (cannabidiol) to treat facial palsy and was worried the sample would come up positive for an innocent reason.

Panel chairman Akbar Khan said: "It is highly improbable the officer believed he had a good reason for failing to comply with a lawful order.

"Harm has undoubtedly been caused to the reputation of the Metropolitan Police Service."

He added that Mr Bennett most likely decided to involve the ex-commissioner "to secure for himself high-level cover to deflect inevitable criticism and embarrassment that would come his way".

The chairman also said that "if the goal of resignation was to avoid embarrassing" the Met this was "unlikely to be achieved".

Outlining the panel's reasons for sacking Mr Bennett, Mr Khan said he had "shown limited insight regarding the proven conduct".

He said this may lead the public to be "concerned his mindset demonstrates an attitude of one rule for senior officers and a different rule for a lower rank officer".

By failing to provide the sample, Mr Bennett was found to have breached force standards for honesty and integrity, orders and instructions and discreditable conduct.

Mr Bennett will appeal against the panel's decision.

His solicitors said in a statement: "The panel found that Cdr Bennett did not take any drugs, cannabis or otherwise.

"The panel found Cdr Bennett guilty of refusing to take a drug test, something he had always admitted.

"The panel also found Cdr Bennett guilty of misconduct that he had not been charged with: this concerns an alleged lack of integrity.

"This finding was despite the prosecution agreeing with the defence that this was not a permissible finding.

"Since Cdr Bennett has been found guilty of a lack of integrity that he had not been charged with, Cdr Bennett has no choice but to appeal so that the sanction decision is retaken on a proper rather than improper basis."

Met Police Assistant Commissioner Barbara Gray said: "Julian Bennett's actions were deplorable. He was a senior officer and showed complete disregard and disrespect for the standards we must all uphold.

"His actions have further damaged not only the public's trust in us as an organisation, but also the confidence of our own officers and staff in those who lead them."