Boris Johnson has urged Russia to stop "acting as a lifeline for Assad's murderous regime" in Syria and instead to "live up to its responsibilities as a global power".
Russia's veto of a UN resolution condemning a deadly chemical attack in Syria and pushing Bashar Assad's regime to co-operate with an international inquiry put the country on the "wrong side" of the argument, the Foreign Secretary said.
World leaders had called for a probe into the "barbaric" attack in Khan Sheikhoun last week, which caused an international outcry and prompted a retaliatory US missile strike.
But Russia, an ally of Syria, blocked a draft UN Security Council resolution which would require President Assad to provide information about air operations and grant inspectors immediate access to air bases.
Mr Johnson said: "The international community sought to make clear that any use of chemical weapons by anyone anywhere is unacceptable and that those responsible will face consequences.
"So I am dismayed that Russia has once again blocked the UN Security Council and in so doing refused to condemn the use of chemical weapons or support a full UN investigation into the attack.
"This puts Russia on the wrong side of the argument."
Mr Johnson backed US calls to find a political solution and said the G7 leaders were ready to work with Russia to end the violence in Syria.
He said: "So Russia faces a choice: it can continue acting as a lifeline for Assad's murderous regime, or it could live up to its responsibilities as a global power, and use its influence over the regime to bring six long years of failed ceasefires and false dawns to an end."
His comments came moments before President Donald Trump said relations with Russia had reached a "all-time low".
He added: "Putin is the leader of Russia. Russia is a strong country. We're a very, very strong country. We're going to see how that all works out."
Mr Trump also backtracked on his criticism of Nato at a joint press conference with its secretary general Jens Stoltenberg, saying: "I said it was obsolete; it's no longer obsolete."
UK ambassador to the United Nations Matthew Rycroft said it was "indefensible" for Russia to support the Syrian regime, as UK scientists in Porton Down confirmed that samples from the scene tested positive for a toxic chemical known as sarin.
The vote came after US Secretary of State Rex Tillerson met his Russian counterpart Sergey Lavrov in Moscow to discuss the escalating tensions in Syria.
The talks got off to a frosty start, with the Russian politician branding the American cruise missile strike "illegal" and criticising "confusing and sometimes openly contradictory ideas" from the Trump administration on the US-Russia relationship and international issues.
Mr Lavrov called for a UN investigation into the attacks in Syria beforehand but no agreement was reached with Washington during the two-hour talks.
Mr Tillerson said there was "a low level of trust" between both countries and such a relationship could not be allowed to continue between the world's foremost nuclear powers.
"We need to attempt to put an end to this steady degradation, which is doing nothing to restore the trust between our two countries or to make progress on the issues of greatest importance to both of us."
Mr Tillerson said there was no doubt that the attack had been planned and executed by the Syrian regime, which has used chlorine bombs on more than 50 occasions.
He said: "Clearly our view is that the reign of the Assad family is coming to an end and they have again brought this on themselves with their conduct in the war over these past few years."