Stella Assange was speaking on the third anniversary of her husband being dragged out of the Ecuadorian embassy in London.
He has since been held in Belmarsh prison in the capital while the US seeks his extradition on espionage charges, which he has always denied.
Protests were held across the world on Sunday in support of Assange, while slogans were projected on to buildings in London calling for his release.
Stella Assange told the PA news agency: “The UK Government could end Julian’s imprisonment at any time by obeying its treaty obligations.
“The US extradition request violates the US-UK extradition treaty Article 4, which prohibits extraditions for political offences.
“The UK Government can and should obey the word of the treaty and put an end to the extradition process once and for all.
“Julian’s incarceration and extradition process is an abuse in itself.
“He faces 175 years buried alive in a US hellhole for publishing true information in the public interest, exposing the crimes and killing of innocent people by the country that wants him to spend the rest of his life in prison.
“The UN special rapporteur on torture has found that Julian has been subjected to psychological torture.
“Senior US officials have reportedly confirmed White House and CIA plans to assassinate him on UK soil during the Trump administration.
“The UK is imprisoning a publisher on behalf of the foreign power who conspired to murder him.
“There is no way of concealing any more that Julian is the victim of a vicious political persecution.
His continued imprisonment is not only a national disgrace, it is a criminal act.”