Russia has been accused of hiring a network of British politicians and consultants to help advance its criminal interests and to "go after" Vladimir Putin's enemies in London, MPs who drew up the Russia report suppressed by Boris Johnson were told.

In secret evidence submitted to parliament's intelligence and security committee (ISC), the campaigner and financier Bill Browder claimed Moscow had been able to "infiltrate" UK society by using well-paid British intermediaries, The Guardian reports.

Some had "reason to know exactly what they are doing and for whom", Browder told the committee. Others "work unwittingly for Russian state interests", he said.

The alleged intermediaries include politicians from both Labour and the Conservative parties, former intelligence officers and diplomats, and leading public relations firms. Collectively, they form what Browder calls a "western buffer network".

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The regime in Moscow uses these professionals to mask its "entangled" state and criminal interests, he alleged. It deploys them to attack Putin critics, "enhance Russian propaganda and disinformation" and to "facilitate and conceal massive money-laundering operations", he said.

With his permission, the Guardian published Browder's previously confidential evidence to the ISC. The committee carried out a two-year investigation behind closed doors into how the Kremlin is seeking to influence and subvert UK politics and society. Its 50-page report was ready for release last November, before the election.

The prime minister was accused of refusing to publish it.

Speaking to the Guardian, Browder said: "Yes, there are members of the Russian security services working out of the Russian embassy under diplomatic cover. What the government seems to be missing is the fact that there are all sorts of informal espionage networks.

"There are Russian oligarchs who have a much greater impact on the security of this country. What's most shocking is that the Russian government is indirectly hiring British nationals to assist them in its intelligence operations."

Browder argues that the Russian state and organized crime have in effect merged. Money stolen from the budget and private companies is used to enrich senior officials – including Putin – and to finance "black ops and special projects".