Jeremy Corbyn was accused of "appeasement" towards Russia as MPs - including his own backbenchers - voiced anger at the Labour leader's apparent reluctance to directly blame Moscow for the Salisbury nerve agent attack.
Mr Corbyn was heckled in the House of Commons on Wednesday as he responded to the Prime Minister's statement setting out a range of retaliatory measures the UK will take against Russia.
The Labour leader described the Salisbury attack as an "appalling act of violence", but urged the Government to ensure its response is "decisive, proportionate and based on clear evidence".
Mr Corbyn also called on Theresa May to maintain "robust dialogue" with Russia, despite her announcement that high-level bilateral contacts are to be suspended.
However, the Labour leader drew ire for failing to explicitly back the Prime Minister's assertion of Russian responsibility for the attack.
Repeating Moscow's demands, he also asked whether Mrs May had accepted the Russian government's request for them to be handed a sample of the nerve agent, in order for them to run their own tests.
Mr Corbyn was then barracked from the Conservative benches for using the exchanges - in which MPs largely supported Mrs May's response to what she branded an "unlawful use of force by the Russian state against the UK" - to suggest the UK's diplomatic capacity has been reduced as a result of cuts.
The PM said: "This is not a question of our diplomacy, of what diplomatic support we have around the world.
"This is the question of the culpability of the Russian state for an act on our soil."
Earlier this week, Mr Corbyn was accused of failing to offer unity and of party political point-scoring in the wake of the Salisbury attack, after he highlighted Russia-linked donations to the Conservative Party.
Mrs May went on to criticise Mr Corbyn's response to her statement, claiming he "could have taken the opportunity - as the UK Government has done - to condemn the culpability of the Russian state".
A number of high-profile Labour backbenchers then voiced their own disapproval with their party leader's comments.
"Can I assure the Prime Minister that most of us on these benches fully support the action she is taking," said former Labour cabinet minister Ben Bradshaw.
Labour's Yvette Cooper, chair of the Home Affairs Select Committee, was cheered by MPs on all sides of the chamber when she said Russia's actions should be met with "unequivocal condemnation".
The PM, in her response, thanked Ms Cooper for the tone of her comments and acknowledged they were "representative of many" on the Labour benches.
Further criticism came from the DUP's Sammy Wilson. He said: "We welcome the decisive action that has been taken by the Prime Minister today and it sits in contrast with the policy of appeasement that we have heard from the frontbench of the Labour Party."
His comments prompted anger from Labour MPs, with Chuka Umunna saying they "do not represent the views of the majority of our voters, members or MPs".
Another Labour MP told Sky News there was "sheer fury" at Mr Corbyn's response.
They said: "He has been briefed on privy council terms. What more evidence does he require?"
https://news.sky.com/story/salisbury-at ... a-11289753Corbyn’s lowest moment. Whose side is he on, COMRADE.
Even the US government has come out strongly against Russia tonight, somewhat surprisingly.