Scotland Yard has admitted Special Branch officers passed information to a controversial network that blacklisted construction workers.

It follows a six-year battle to find out if the Metropolitan Police supplied the intelligence on trade unionists.

The force says its investigation had “proven” the allegation, which will be investigated by a public inquiry.

Workers who say they were unfairly barred from jobs have already received millions of pounds in compensation.

In 2016, the union Unite reached a settlement with construction firms that resulted in 256 workers sharing more than £10m in compensation.

At the heart of the claims, which were made by hundreds of workers, was evidence that firms accessed a “blacklist” that logged workers’ trade union activities.

The list was used by dozens of construction firms to vet those applying for work on building sites.

When the files were found to contain details of individual’s political activities, the workers demanded that Scotland Yard disclose whether undercover police had colluded in supplying intelligence.

………

In a letter to the workers’ lawyers, Deputy Assistant Commissioner Richard Martin said the findings of the Metropolitan Police’s internal investigation, completed two years ago, were so sensitive that they were sent directly to the then commissioner.

The letter states: “Allegation: Police, including Special Branches, supplied information that appeared on the Blacklist, funded by the country’s major construction firms.

“The report concludes that, on the balance of probabilities, the allegation that the police or Special Branches supplied information is ‘proven’.

This scheme did not spring full grown from the forehead of  the Yard.

Politically connected builders leaned on elected officials, who in turn leaned on law enforcement.

Hopefully, this will be investigated more deeply.