Downing Street has taken a swipe at Russia over its record on human rights, freedom of speech, the economy and the war in Syria, in response to its embassy's claims that Britain was preparing an "official witch-hunt" against the Putin regime.
In an attack posted on its website on Tuesday, the Russian embassy in London claimed "Western elites" were in "panic and hysterics" over their loss of control in Europe, and accused Britain of planning to brief Donald Trump's incoming US administration against Moscow.
The outburst came as US media published a dossier containing allegations - denied by Moscow - that Russian intelligence agencies have gathered a file of compromising information about the president-elect, who will meet Theresa May for the first time when she visits the US in the spring.
It followed Foreign Secretary Boris Johnson's claim in the House of Commons that Russia was "up to all sorts of very dirty tricks" such as cyber warfare.
Mrs May's official spokeswoman declined to comment on the Trump dossier published by the US media, which was reported to have been compiled by a former British intelligence officer and passed to American agencies.
In response to the Russian embassy statement, the PM's spokeswoman said: "If you want to look at the record of the UK Government in recent years and make comparisons with the Russians, you might think about n egative economic growth in Russia and the UK being one of the fastest-growing major economies in the world; h ow many times the UK has consistently advanced and supported UN Security Council resolutions on Syria - I think Russia was meanwhile vetoing them; t he fact that we have freedom of expression and a free press in the UK who will choose what they report.
"Those are just the realities of the UK Government versus the Russians. You ought to look at what the UK Government's record of actions are and what the Russian record of actions are."
Meanwhile, a senior Labour source called for a "ratcheting down" of tensions between Russia and the West, particularly on the border between Nato countries and Russia and in the Middle East.
In its lengthy post, the Russian embassy speculated Mrs May's Government was seeking to rerun the Brexit referendum by claiming it was tainted by Russian influence and attacked the British intelligence services.
The embassy also suggested the UK's loud condemnations of Russian military action in Syria were intended to divert attention from its "complicity in the deliberate obliteration of Yemen".
It claimed Britain had "outsourced" the fight against Islamist extremism to Russia in the same way the defeat of Nazi Germany was "outsourced" to the Soviet Union.
"We don't expect HMG (Her Majesty's Government) to win this argument in an open and reasoned debate," said the post. "We also think that it is plainly wrong for one UNSC (UN Security Council) permanent member to brief against another."
The Labour source said Jeremy Corbyn had repeatedly voiced criticisms of the Russian government over its actions in the Middle East and domestically.
But he added: "What we don't want to see is a ratcheting up of tensions between Russia and the West, as has been taking place. We want to see an engagement with Russia - on a critical basis, but a serious basis."
The source said Mr Corbyn had "expressed concerns" about the deployment of hundreds of UK troops to Russia's neighbour Estonia, where RAF Typhoon fighter jets have also been involved in the interception of Russian warplanes.
" We've said repeatedly that we want talks and engagement to wind down military tensions, particularly on the Nato/Russian border and in the Middle East," said the source.
"Jeremy has expressed concerns about that being one of the escalations of tensions that have taken place."