Boris Johnson looks "daft" and is in "deep political trouble" after pulling out of a meeting with the Russians following a discussion with the United States, it has been claimed.
Secretary of State Rex Tillerson will go ahead with a planned trip to Moscow to deliver a "clear and co-ordinated" message to the Kremlin over its support for Bashar Assad's Syrian regime.
But the move makes the Foreign Secretary look like "some sort of mini-me" who cannot be trusted to hold his own talks with Russian counterpart Sergey Lavrov, Alex Salmond said.
The SNP's foreign affairs spokesman told BBC One's Andrew Marr Show: "Boris Johnson just looks daft.
"What is the argument for not going ahead with a visit? Rex Tillerson is going on Wednesday so it can't be that we have moved to a Cold War position of no talking whatsoever.
"The idea the Foreign Secretary can't be trusted because he might pursue his own line or have an independent thought or crossover what the Americans are going to say just makes him look like some sort of mini-me to the United States of America.
"That's not a position any Foreign Secretary would want to be in."
"Boris Johnson looks in deep political trouble this morning," he added.
Russia has consistently denied that Syrian forces used chemical weapons, insisting the incident at Khan Sheikhoun was caused by a hit on a rebel chemical weapons plant, a claim dismissed by the West.
Mr Johnson will push leading nations to demand Russia withdraws its forces from Syria when he meets G7 counterparts for talks in Italy next week.
International Development Secretary Priti Patel said Mr Johnson was focused on working with allies to find a solution to the crisis.
She told Marr: "This isn't just about one voice, this is about the international community coming together and our Foreign Secretary is working with his American counterpart as that is the right thing to do."
Pressed on why the UK had pulled out of talks with Moscow, she replied: "We are constantly engaging with all our counterparts and there has been dialogue. The Foreign Secretary has engaged his counterpart previously as well."
Mr Johnson said developments in Syria had "changed the situation fundamentally" as he dropped out of the planned talks with Mr Lavrov.
"We deplore Russia's continued defence of the Assad regime even after the chemical weapons attack on innocent civilians," he added.
"We call on Russia to do everything possible to bring about a political settlement in Syria and work with the rest of the international community to ensure that the shocking events of the last week are never repeated."
In January, Mr Johnson said Assad should be allowed to run for election to remain in power in Syria and warned that Britain may have to ''think afresh'' about how to handle the crisis after failing to live up to its mantra that the dictator must go.
But sources insisted he has always believed Assad cannot remain in power.