Oligarchs will be prevented from using their “deep pockets” to silence critics, Dominic Raab has said.

The Justice Secretary promised measures, to be announced shortly, that will prevent oligarchs close to Vladimir Putin from exploiting UK courts and libel laws to sue investigators or journalists who exposed their “excesses”.

It is expected that Mr Raab will seek to limit the costs oligarchs’ critics might face from court actions, which could bankrupt them.

Speaking during a visit to Britain’s newest prison in Wellingborough, Northamptonshire, he pledged to protect free speech in his proposed new Bill of Rights.

Mr Raab, the Deputy Prime Minister, also suggested that the UK stood ready to jail Putin for war crimes if that was needed, citing the precedent of Britain imprisoning the Bosnian Serb leader Radovan Karadzic and Charles Taylor, the Liberian warlord.

He warned that Britons may have to accept higher energy prices rather than allowing the UK to be cowed and blackmailed over gas supplies by Putin.

The legal actions are known as Slapps – strategic lawsuits against publication participation – or lawfare.

Mr Raab said: “Here in the Ministry of Justice, what we are not going to tolerate is people exercising freedom of speech legitimately and people with decent honourable reputations being subject to libel claims by those with deep pockets who can ruin them in the process.

“I am going to look at Slapps and say something about that relatively soon. We will not have people close to Putin coming here to try and bankrupt people who shine a light on his excesses.

“It’s about oligarchs and kleptocrats who get together and try to sue people who shine a light [on their affairs].”

It comes after the High Court on Wednesday threw out a libel claim by a Kazakh mining group over a book on dirty money by the journalist Tom Burgis.

‘We need to wean ourselves off Russian gas’

On energy costs, Mr Raab said: “I don’t think as a country – notwithstanding the impact that this will have on overall energy prices – I don’t think that we can be cowed when a point of principle like this comes up and we will have to take these sanctions measures.

“At the same time, of course, we work with our international partners to wean Europe – much more than the UK, it has to be said – off energy supplies from Russia…we can’t let Putin hold the world to ransom with his gas and energy supplies.”

Asked whether Britain was prepared to take Putin into one of its jails as war criminal, he said: “Look, we have done this before – Charles Taylor, Karadzic. If Milosevic had survived he would have come to a high security prison.

“Of course I wouldn’t want to prejudice any step of the legal process. What I’m saying is with our allies around the world – particularly ones who support the International Criminal Court – it’s not just a court, it’s an international justice system. And we all need to work together to make sure there is a credible deterrent effect.

“We do that by supporting the court on everything from information cooperation, witness relocation, forensics to sentence enforcement [taking war criminals into UK jails]. No one has done more than the UK in that regard.”