In an interview with The Guardian, Anwar, who was released from prison after the opposition won power for the first time in Malaysia, said the previous government had used the savings of ordinary people to cover up the multibillion-dollar embezzlement scandal at 1MDB, a state investment fund.

“All these deals which are considered dubious, including investments in housing in London, will have to be investigated.

“Yes, that includes Battersea. Because they were made using state funds. We have to be convinced that this was the right investment decision and that there was no political influence or direction [within Malaysia],” he said.

“It’s clearly a political decision to invest. If there is something wrong then we will want to renegotiate. We are looking at umpteen deals extending to hundreds of billions of ringgit – that is tens of billions of dollars.

“You look at every deal from housing in London to railways built by China. It’s baffling to me and I was monitoring the policies of [the former prime minister] Najib [Razak] and attacking him ferociously. But even I am shocked to the extent he seems to have gone to earn more to cover up the 1MDB fiasco.”

Najib denies any wrongdoing.

The current government said more than US$4 billion was stolen from a government fund, with an alleged $681 million ending up in Najib’s personal bank account.

There has recently been a series of raids on Najib-linked properties in which 284 Hermes handbags and 72 bags of cash, watches and jewellery were seized.

Anwar’s comments will raise questions about the British government’s commitment to fighting corruption.

He said the money trail of the 1MDB fraud ran through London, with US$1.83 billion of Malaysia’s cash funnelled into a Saudi-British company.

“There was no attempt by British authorities to investigate. But this was a crime using sovereign wealth funds for reckless spending sprees. I am seeking support from the British government and from the foreign secretary, Boris Johnson,” he said.

Anwar backs Mahathir’s review of Chinese deals – but not to annoy Beijing

“I say to Britain: you talk about transparency and anti-corruption drives, now is the time for action. I am saying now allow the institutions to conduct investigations fairly and give the necessary cooperation.”

Anwar pointed out that in Singapore, people have gone to prison and banks have been closed down for their role in laundering 1MDB cash.

“Look, the last Malaysian government did not want the British to be involved. But we are now giving them a mandate to investigate,” he said.

The opposition leader spent nine years in prison on charges that he insists were politically motivated, having been jailed on two occasions, including in 1999 by Malaysia’s prime minister, Mahathir Mohamad.

Malaysia’s PM Mahathir urges TPP ‘renegotiation’ during trip to Tokyo

Anwar said he trusted Mahathir to pursue their shared reform agenda and had forgiven him.

“I will be returning to politics soon. I always refrained from giving a time frame to my return because it would render the prime minister’s position as untenable. He would be a lame duck. What I want to give him is my full support to make tough decisions with the full force of the law,” he said.

The Battersea project is 17 hectares (42 acres) and includes more than 4,000 new homes.

Malaysian state-owned companies are the developers of the other five phases of the project, which is due to be completed by 2028. When contacted, the Battersea Power Station Development Company said it had no comment to make.

A government spokesperson said: “The UK has a robust legal and regulatory framework which enables effective investigation of suspected money laundering, corruption and the recovery of illicit assets, and we continue to work closely with international partners to stem the flow of illicit wealth.”