A total of 33 Labour MPs have so far put their names to a motion insisting Russia did carry out the poisoning of former Russian spy Sergei Skripal and his daughter, Yulia.
It's a clear challenge to Labour leader Jeremy Corbyn , who has insisted it's still not clear who is responsible for the nerve agent attack in Salisbury - and suggested "Russian mafia-like groups" could be involved.
West Midlands MPs signing the Commons motion include Ian Austin, Labour MP for Dudley North; Adrian Bailey, Labour MP for West Bromwich West, and John Spellar, Labour MP for Warley.
Their motion states that the group of MPs "unequivocally accepts the Russian state's culpability for the poisoning of Yulia and Sergei Skripal in Salisbury using the illegal novichok nerve agent which has also led to the serious illness of Detective Sergeant Nick Bailey who went to their rescue, and to the possible poisoning of other members of the emergency services and public as yet unknown."
And it "fully supports the statement made by the Prime Minister on 14 March 2018 in response to Russia's illegal attack on the UK."
It's a contrast with the position taken by Mr Corbyn. Writing in the Guardian on Thursday, he said the idea that the Russian state was responsible was just one possibility.
He said: "Either this was a crime authored by the Russian state; or that state has allowed these deadly toxins to slip out of the control it has an obligation to exercise.
"If the latter, a connection to Russian mafia-like groups that have been allowed to gain a toehold in Britain cannot be excluded."
And he suggested more evidence was needed before a conclusion could be reached. Mr Corbyn said: "To rush way ahead of the evidence being gathered by the police, in a fevered parliamentary atmosphere, serves neither justice nor our national security."
Backbench Labour MP Chris Williamson, an ally of Jeremy Corbyn, has described Labour MPs signing the motion as "political enemies".
He was speaking earlier in the week when just 18 Labour MPs had signed the motion. HuffPost UK reports he criticised Conservatives, and added: "Regrettably we have a few on our own benches who are like-minded, 18 of them have signed an Early Day Motion (EDM) saying they unequivocally accept Russia are responsible for the attack.”
Mr Williamson is reported to have told a meeting of Momentum, an organisation which supports Jeremy Corbyn: "It would definitely be helpful, I think, for our own people on the green benches to actually fall in behind the leader's very statesmanlike and measured response.
“It only helps our political enemies. But frankly I see them as political enemies as well.”
He suggested the MPs should be deselected, which would mean they were barred from standing as Labour candidates at the next general election.
“I have been advocating for a long time now for mandatory re-selection.
“We mustn’t allow the tiny minority of irrelevant malcontents that sit on the green benches on the House of Commons to deter party members.”