Corrupt police in the Flying Squad were suspected of plotting to kidnap the partner of a cash van driver to obtain a £50,000 ransom, secret intelligence reports obtained by the BBC reveal.
According to the documents, a group of London-based officers hatched the plot in the mid-1990s.
Police sources told the BBC the reports were part of a "lorry-load" of documents thought shredded by the Met.
The Met said it does not comment on leaked intelligence reports.
The documents say the plot began after the cash-driver's partner was kidnapped by bank robbers.
The driver was ordered to go to his depot and fill a suitcase with £50,000 to secure her release - a style of heist known as a "Tiger kidnap".
Five days later officers from the Flying Squad began to investigate.
But the reports claim officers then decided to repeat the plot themselves - targeting the same driver and his partner once again.
Already involved in probing the first crime, they knew they would be tasked with investigating any second, identical offence.
This meant they would in effect be investigating themselves - so they could get away with the crime.
The intelligence reads: "Information was received that officers attached to the Flying Squad were involved in the planning and commission of armed robberies and other criminal acts.
"The van driver was to be approached and shown a ring belonging to his wife."
When anti-corruption police learned of the conspiracy the officers were investigated and their phones were tapped.
Their investigation forms the basis of the two intelligence reports obtained by the BBC.
One of the reports continues: "It was learned the next robbery was planned... when the driver would be attacked as he parked his vehicle.
"His house keys would be taken and one of the 'gang' would leave and return with his wife's ring and tell the driver she would be hurt if he did not do as instructed.
"This scenario has allegedly been used on one other occasion by the officer when he netted £40,000."
It goes on: "General information is [the informant] was introduced to this officer about 18 months ago. [The informant] has a gun for which the officer supplied him with 100 bullets.
"He [one of the officers] was also supplied with a grenade."
It is understood that at this point the officers abandoned the plot after becoming aware of anti-corruption investigations.
Police had been hoping to arrest them when they attempted to execute the kidnap. When this did not happen there was not enough evidence to prosecute.
Several police sources have corroborated to the BBC that the reports are genuine.
The disclosure comes weeks after a mass shredding of documents relating to a corruption inquiry in the Metropolitan Police was revealed.
The "lorry-load" of material was shredded over two days. It was related to an anti-corruption inquiry that began in 1993 and continued for a lengthy period of time.
The BBC asked the Met whether it could find and account for the two intelligence reports.
The force is understood to have found one of the reports backed up on computer.
At the time of publication the Met has not been able to find the other report, despite having been made aware of the issue five days ago.
London Assembly Member Jenny Jones, who sits on the Police and Crime Committee, said: "It sounds more like the plot of a bad police film than anything you would connect to the Metropolitan Police.
"It's also very concerning the information was apparently lost in the police shredding.
"The commissioner is going to have to make a clear statement on these matters."
One of the allegedly-corrupt officers mentioned in the intelligence reports was known to be friendly with those suspected of murdering Daniel Morgan.
Mr Morgan was killed with an axe in a pub car park in 1987 before he could blow the whistle on police corruption.
His brother Alastair said of the latest disclosures: "Why has it been kept in the dark so long?
"And if this is a widespread phenomenon, how much else has been buried? We just don't know."
The BBC has now traced the kidnap victim, who was unaware she was the target of a suspected corrupt police plot.
She is now considering legal action against the Met.
A Met spokeswoman said: "The nature and scale of corruption within the MPS in the 1990s was recognised at the time as entirely unacceptable.
"The fight against corruption was carried out with determination, vigour and innovation.
"The result was a number of corrupt police officers went to prison or were sacked from the MPS."
She added: "We have already accepted that historically the Met did not keep good records of what was retained or destroyed.
"We are determined to ensure that records are now fit for purpose."
The Met said it was confident it held intelligence on the officers named in the reports.
The spokeswoman added: "It must be deeply disturbing to hear from the media, nearly 20 years on, you were the intended target of a kidnap plot.
"In the modern day MPS, victim care is of the utmost importance."