Britain's Labour Party leader Jeremy Corbyn says London should not extradite Julian Assange to the United States

A man holds a placard against Ecuadoran President Lenin Moreno as he demonstrates against the arrest of WikiLeaks founder Julian Assange in front of the Foreign Ministry in Quito on April 11, 2019. (AFP photo)

The leader of Britain's opposition Labour Party, Jeremy Corbyn, says the UK government should oppose the extradition of WikiLeaks founder Julian Assange to the United States, following his forcible removal from the Ecuadorian embassy in London.

Corbyn said in a tweet on Friday that the US is trying to extradite Assange because he exposed US war crimes in Iraq and Afghanistan.

"The extradition of Julian Assange to the US for exposing evidence of atrocities in Iraq and Afghanistan should be opposed by the British government,” he wrote.

The Australian whistleblower was arrested on behalf of the US on Thursday at the Ecuadorean embassy in London, where he had been granted asylum since 2012.

Assange, 47, is wanted by the US government for publishing classified documents related to the Iraq and Afghanistan wars that were leaked by American whistleblower Chelsea Manning.

Labour's spokeswoman for domestic affairs, Diane Abbott, told the BBC on Friday that the government should block the extradition on human rights grounds.

Abbott says the U.S. case against Assange is about the "embarrassment of the things he's revealed about the American military and security services."

She says Assange is "a whistleblower, and much of the information that he brought into the public domain, it could be argued, was very much in the public interest."

UK Prime Minister Theresa May and several cabinet ministers, including Home Secretary Sajid Javid, welcomed the arrest.

Assange spent seven years at the Ecuadorian embassy in London before being detained on a US extradition warrant and for breaching bail.

The 47-year-old faces up to 12 months in a British prison for breaching his bail conditions.

He then faces extradition to the US to face charges that he conspired to hack into a classified US military computer, which carries a maximum sentence of five years.

But WikiLeaks editor Kristinn Hrafnsson said he fears more charges will be added once Assange arrives in the US, meaning he could face decades in an American prison.

Legal experts say the US extradition fight could last for years, given that his previous battle against extradition to Sweden to face rape allegations took 18 months.

Ecuador's president, Lenin Moreno, said in July that he was planning to withdraw asylum protection for Assange and evict him from its UK embassy.

Assange was granted asylum by Ecuador’s former president Rafael Correa, after he took refuge in the country’s embassy in 2012. Moreno, however, revoked the asylum and allowed police to arrest him.