Jeremy Corbyn has said he would still do business with Russia despite “all fingers” pointing towards the country being responsible for the Salisbury spy incident.

The Labour leader has been forced to defend his stance on the attack after declining to categorically blame the Kremlin for the poisoning of Sergei Skripal and his daughter, Yulia, on March 4.

Mr Corbyn’s earlier warning not to “rush ahead of the evidence” led to criticism from Conservatives and some Labour backbenchers, however he reiterated his call for Russia to be sent samples of the nerve agent to discover its source.

He told Radio 4’s World at One: “All fingers point towards Russia’s involvement in this, and obviously the manufacture of the material was undertaken by the Russian state originally.

“What I’m saying is the weapons were made from Russia, clearly.

“I think Russia has to be held responsible for it but there has to be an absolutely definitive answer to the question where did the nerve agent come from? I asked the Russians be given a sample so that they can say categorically one way or the other.”

G20 meeting – Germany
Russian president Vladimir Putin (Matt Cardy/PA)

Mr Skripal, a former double agent, and his daughter are still fighting for their lives after being exposed to Novichok in the Wiltshire city.

Shadow chancellor John McDonnell has previously said Labour agreed with Theresa May that Russia was responsible for the attack.

But Mr Corbyn maintained there had to be a relationship with Russia and said he would still “do business” with President Vladimir Putin if Labour came into power.

“Would I do business with Putin, sure? And I’d challenge him on human rights in Russia, challenge him on these issues and challenge him on that whole basis of that relationship,” he told the BBC.

Salisbury incident
Police at The Maltings shopping centre, where Sergei Skripal and his daughter Yulia were found critically ill (Ben Birchall/PA)

On Monday, Mrs May hit back at Mr Putin’s dismissal of the British Government’s claim that Russia was responsible for the attack.

Her comments followed strong words from Boris Johnson, who accused Russia of trying to conceal “the needle of truth in a haystack of lies” over the case – after Mr Putin dismissed the idea of Russian responsibility as “nonsense”.

Writing in the Daily Telegraph, the Foreign Secretary said the use of a nerve agent against the Skripals was “very deliberate”.

“As Ken Clarke pointed out in Parliament last week, the obvious Russian-ness of the weapon was designed to send a signal to anyone pondering dissent amid the intensifying repression of Mr Putin’s Russia,” he wrote.

“The message is clear: we will hunt you down, we will find you and we will kill you – and though we will scornfully deny our guilt, the world will know that Russia did it.”

Mr Corbyn’s interview with Radio 4’s World at One will be broadcast on Tuesday.

Meanwhile, the National Security Council is meeting on Tuesday to review the Salisbury situation and decide whether to take any further action against Russia over the incident.