Shadow chancellor John McDonnell has told ITV's Peston on Sunday he backs Theresa May's action against Russia - while defending Jeremy Corbyn's response to the Salisbury ex-spy poisoning.
Mr McDonnell said: "We support exactly what the Prime Minister said and we condemn Russia for this. I believe this is a pattern of behaviour we have seen."
He then told Robert Peston, "whichever way you look at it (Vladimir Putin) is responsible".
In doing so, he appeared to contradict the line of the Labour leader - who had been initially reluctant to blame the Kremlin directly.
Yet Mr McDonnell said Labour had been "clear and consistent" in condemning Russia.
Reacting to Labour divisions over Mr Corbyn's response to the incident, Mr McDonnell said the Labour leader had given a "constructive critique" and others "had misread that".
Mr Corbyn had faced jeers from his own benches along with the government side in midweek as he raised doubts about who was responsible for the Salisbury nerve agent attack.
The Labour leader on Saturday said the Russian authorities "must be held to account on the basis of the evidence and our response must be both decisive and proportionate".
Mr McDonnell appeared to go further on Peston on Sunday, saying the Salisbury incident is "highly likely" to have been a state execution.
When asked if he pointed the finger directly at the Russian president, Mr McDonnell said: "He is responsible whichever way you look at it, he is responsible and all the evidence points to him."
The shadow chancellor united behind Mr Corbyn's call to "stop serving Russian crony capitalism" as he said hitting Russians "in their pockets" was the most effective response beyond diplomat expulsions as he called for a tax measure on property.
But Mr McDonnell played down a description of it as an "oligarch's levy" and said the action could be achieved by fulfilling Labour's election pledge to put a levy on properties owned by foreign companies.
"It's not specifically for Russian oligarchs," he said, but added Russians made up "at least a quarter" of those who would be affected.