Senior MPs have backed calls for the Foreign Office to do more to help a British citizen jailed for 25 years in Russia for opposing the invasion of Ukraine.

British-Russian dissident Vladimir Kara-Murza was sentenced to 25 years in prison in April, after he had been convicted of high treason by a Moscow court.

Mr Kara-Murza has already survived two poisoning attempts by Russian agents, and has developed a medical condition that has deteriorated during his imprisonment to the point where he has lost feeling in his feet and one of his arms.

His wife, Evgenia Kara-Murza, now fears that he will die if he is not released from prison and has called for more action from the British government.

Describing her meetings with Foreign Office ministers, she said: “Everything that was said in these meetings were the right words, I just would like to see some action.”

Mrs Kara-Murza’s calls have received cross-party support from MPs including Labour’s Sir Chris Bryant and Tories Bob Seely and Alicia Kearns, chair of the Foreign Affairs Committee.

Ms Kearns said whether the Foreign Office could keep British citizens safe and get them home when it needed to was a test of its “fundamental effectiveness”.

She told the PA news agency that she is calling for the creation of a Director for Arbitrary and Complex Detentions within the Foreign Office to lead on hostage negotiations.

“The UK’s response to the illegal detention of Vladimir has been appalling, for complex cases like this where the charges are politically motivated, we need someone who can cut through Whitehall bureaucracy and get our people home,” she said.

“Despite Putin’s descent into maniacal authoritarianism, despite the hell that Russia has unleashed in Ukraine, there are pockets who continue to believe a different Russia, a better Russia, is possible,” Ms Kearns added. “Vladimir is one such man. This is why we fight for him. We remember him, we shout his name and we raise hell wherever possible.”

Mr Seely said: “What’s absolutely critical is that we continue to press this case with the Foreign Office, to encourage the Foreign Office to take a high-profile stance.

“What slightly worries me is that despite being a British citizen, Vladimir Kara-Murza seems to be getting as much support from the US, Canada and other countries.

“He is a British citizen, he was brought up here, and even though his heart is in Russia and he is fighting authoritarianism in Russia for a better future for Russians, we need to be much more vocal about not only the case of political prisoners but especially when political prisoners have British passports.”

The United States has sanctioned several individuals involved in Mr Kara-Murza’s prosecution, and Canada has awarded him honorary citizenship to allow them to take up his case directly with the Russian government.

Sir Chris said: “It’s time the UK Government really got its act together and made serious and urgent representations on behalf of Vladimir, who has a UK passport.”

In April, the Government sanctioned five of the people involved in Mr Kara-Murza’s imprisonment, but now his wife is calling for the Foreign Office to establish a directorate for hostage affairs to pro-actively advocate for British citizens arbitrarily detained abroad.

She said: “Creating this office of hostage affairs in democratic countries would arm these democratic countries to deal with this ever-rising crisis of hostage taking all over the world.”

The United States already has a similar office, which has been able to secure the release of hostages including basketball player Brittney Griner, and the Foreign Affairs Committee recommended creating a British version in a report published in April.

Bill Browder, a friend of Mr Kara-Murza and head of the Global Magnitsky Justice Campaign, also backed Mrs Kara-Murza’s campaign.

He characterised the Foreign Office’s current approach as “delivering magazines and warm socks” and called for a more pro-active response.

Referring to the case of Nazanin Zaghari-Ratcliffe, who was imprisoned in Iran for six years, he added: “Nazanin’s husband should not have had to go on hunger strike to get the Foreign Office to do anything.”