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.

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”.

There is no suggestion in Browder’s testimony that British citizens broke the law.

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.

Putin’s spokesman Dmitry Peskov called Browder’s claims false and “totally groundless”. Questions about corruption at the heart of the Russian state were “a perfect example of a maniac-style Russophobia”, Peskov said.

With his permission, the Guardian is publishing 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.

Downing Street cleared the document after the election. It claims the final document contains little new information and is underwhelming – although others who have read it disagree.

Opposition MPs said Browder’s evidence demonstrated the need to publish the report as soon as possible.

Ian Blackford, the leader of the SNP at Westminster, wrote to Johnson a month ago asking for a timetable for the report’s publication, which requires Downing Street to appoint a new nine-member cross-party committee of MPs and peers.

But nearly three months after the election, that process is only in its early stages, and it is likely to be a few weeks at least before the long-awaited report is able to be issued, partly because new members need to be vetted before they can sit.

Browder was one of several expert witnesses invited to give evidence to MPs and peers. In September 2018 he submitted a 14-page statement, which included a number of recommendations.

They include setting up a US-style register of individuals working for foreign state interests, as well as extra resources for regulators, investigators, police and prosecutors. He calls on Companies House in London to review filings made by firms linked to Russian money-laundering scandals.

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 organised 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”, he told the ISC.

The Kremlin has issued multiple Interpol warrants for Browder’s arrest and says he is a criminal. It has convicted him in absentia of tax evasion and deliberate bankruptcy. Browder says he is the victim of a vendetta by corrupt state officials. He denies all charges.

Browder’s fund, Hermitage Capital Management, was once the biggest foreign investor in the Russian market. He fell out with the authorities after – he says – calling for a clean-up of companies in which Putin and his inner circle have financial interests. In 2005 Russia deported him from Moscow.

Officials linked to the FSB spy agency subsequently stole $230m in taxes paid by the fund to the Russian treasury, Browder alleges. In 2009 his lawyer Sergei Magnitsky died in custody. Browder persuaded the US and some other western governments to sanction senior officials allegedly involved in human rights abuses.

The Kremlin was furious. It paid British firms to “advance a false narrative of the fraud”, Browder told the ISC. One official allegedly involved, Andrey Pavlov, made an unsuccessful attempt to keep his name off a European parliament sanctions list, hiring the Labour former attorney general Lord Goldsmith to lobby on his behalf. Goldsmith’s law firm received a £75,000 fee, Browder claims.

The firm, Debevoise & Plimpton, said it could not comment on confidential client matters but that Pavlov denied wrongdoing. It added: “Everyone is entitled to legal representation. Debevoise provides legal representation consistent with the profession’s best traditions of integrity and probity. We will continue fearlessly to defend the interests of all our clients.”

Pavlov retained the services of GPW, a business intelligence company run by a former MI6 officer, Andrew Fulton. Browder says GPW’s brief included gathering intelligence on him. Fulton – a chairman of the Scottish Conservative party – left GPW in 2017. Its managing director, Philip Worman, said he could not comment on “any aspect of our work”.

Fulton’s former GPW colleague Andrew Wordsworth said Pavlov was entitled to know the facts of his case: “The use of sanctions against individuals is a pretty draconian remedy. Some people would argue that before you destroy people’s lives they should be able to defend themselves.”

In his evidence Browder alleges that Pavlov also hired Lynton Crosby’s communications firm CTF, paying it £45,000.

However, CTF denies Browder’s allegations. It says Goldsmith’s law firm hired a separate entity, CTF Corporate & Financial Communications (CTFCFC), to “research the EU sanctions landscape”. CTFCFC advised the law firm and there was no contact with Pavlov. “This was the extent of our involvement and to try and claim otherwise would be utterly false,” it said. According to Companies House records, Crosby is a CTFCFC director.

There is no suggestion Crosby personally worked on or was aware of the work on EU sanctions carried out by CTFCFC until it appeared in the media. “Lynton Crosby was working exclusively on the 2015 general election campaign for the Conservative party at this time, and had no client involvement, outside of the Conservative party,” it said, adding that Crosby had never met or worked with Goldsmith or Debevoise.

Browder further names British individuals who have fronted up offshore companies used in the alleged Magnitsky fraud and in other cases. The UK citizens appear as nominal directors of non-transparent firms in countries through which billions of dollars have been laundered, including the UK, Russia, Ukraine, Cyprus and Latvia.