Jeremy Corbyn has called for the extradition of Julian Assange to the US to be halted, praising the Wikileaks founder for exposing US “war crimes”.

Boris Johnson refused to comment on the case, which will begin this month – but surprised the Commons by agreeing the extradition treaty between the two countries is “unbalanced”.

The Labour leader’s call came as he also demanded to know whether Anne Sacoolas, who drove the car that killed teenager Harry Dunn, is being “shielded” because she was a CIA spy.

On Mr Assange, who faces up to 175 years in a US jail if convicted, Mr Corbyn backed MPs on the Council of Europe who have warned the extradition “sets a dangerous precedent for journalists”.

The one-sided arrangements would be “laid bare” when the courts decide whether he should be sent to the US on “charges of espionage for exposure of war crimes, the murder of civilians and large-scale corruption”, he said.

“Will the prime minister agree with the parliamentary report that’s going to the Council of Europe that this extradition should be opposed and the rights of journalists and whistleblowers upheld for the good of all of us,” Mr Corbyn demanded.

In response, the prime minister said: “I’m not going to mention any individual cases but it’s obvious that the rights of journalists and whistleblowers should be upheld and this government will continue to do that.”

Mr Assange, who is being held in London’s Belmarsh prison, has been indicted on 18 charges – 17 under the Espionage Act – for conspiracy to receive, obtain and disclose classified diplomatic and military documents.

Among Wikileaks’ revelations was video footage from a 2007 US Apache helicopter attack in Baghdad that killed at least nine men, including a Reuters news photographer and his driver.

Key moments for Julian Assange Show all 9 1 /9 Key moments for Julian Assange Key moments for Julian Assange The situation today Assange was arrested after Metropolitan Police officers were invited into the Ecuadorian embassy on April 11 2019. How did it come to this? Ruptly TV Key moments for Julian Assange The break Assange shows the front page of the Guardian on July 26 2010, the day that they broke the story of the thousands of military files leaked by WikiLeaks AFP/Getty Key moments for Julian Assange Wanted A warrant for Assange's arrest was issued in August 2010 for counts of rape and molestation in Sweden AFP/Getty Key moments for Julian Assange Ruling The UK's Supreme Court ruled in 2012 that Assange should be extradited to Sweden to face trial Getty Key moments for Julian Assange Sanctuary Following the ruling, Assange was given asylum by the Ecuadorian governement over fears that his human rights would be violated if he were extradited, he has since remained in the embassy in London Getty Key moments for Julian Assange A friend in Pam Friend Pamela Anderson delivers lunch to Assange at the embassy in October 2016. She has since spoken against his arrest Getty Key moments for Julian Assange Arbitrarily detained A UN panel found in 2016 that Assange had been arbitrarily detained and that he had not been able to claim his full right to asylum. It urged Sweden to withdraw the charges against him Getty Key moments for Julian Assange The cat ultimatum Last year, the Ecuadorian embassy threatened to revoke Assange's internet access unless he stopped making political statements online and started taking better care of James, his pet cat. Assange accused Ecuador of violating his rights Reuters Key moments for Julian Assange Arrest Assange was arrested on April 11 2019. Ecuador revoked his asylum status and invited the Metropolitan Police in to the embassy to arrest him. Reuters

The MPs’ report backs the recommendation of the UN special rapporteur on torture who called last year for the extradition to the US to be blocked.

On the claim that Ms Sacoolas “is in fact a CIA operative”, Mr Corbyn claimed: “Now we know the foreign secretary [Dominic Raab] misled the Dunn family, who are being denied justice by the US government, will the prime minister commit to his removal from office tomorrow in his reshuffle?”

Mr Johnson replied: “The Foreign Office has been told Anne Sacoolas was notified to the UK government as a spouse with no official role.

“We will continue without fear or favour to seek justice for Harry Dunn and his family and continue to seek the extradition of Anne Sacoolas from the United States.”

Mr Corbyn protested: “This lopsided treaty means the US can request extradition in circumstances that Britain cannot.”