The former Russian double agent left close to death after a nerve agent attack in Salisbury had written to President Vladimir Putin asking to be pardoned and to be allowed to visit his home country, a friend has claimed.

Vladimir Timoshkov, a friend of Sergei Skripal, said he regretted having spied for the British and wanted to return to Russia to visit his family.

In 2006 Colonel Skripal was jailed by the Russian for selling secrets to MI6 and came to Britain in 2010 as part of a spy swap, setting up home in Salisbury.

He remains in a critical condition with his daughter Yulia, three weeks after they were poisoned with the highly lethal nerve agent Novichok.

The attempted assassination sparked a diplomatic crisis between Russia and Britain.

On Friday, EU leaders promised an "unprecedented" diplomatic response to the attack after backing Theresa May's assertion that Moscow was responsible.

According to Mr Timoshkov, who says he had known him since school, Col Skripal, 66, did not see himself as a traitor as he had sworn an oath to the former Soviet Union.

"Many people shunned him. His classmates felt he had betrayed the Motherland," he told the BBC. "In 2012 he called me. We spoke for about half an hour. He called me from London.