Britain on Saturday accused Moscow of pursuing a new "diversionary tactic" over last month's poisoning of an ex-spy in the English city of Salisbury, as it considers a request by Russia's Ambassador in London for a meeting with Foreign Secretary Boris Johnson.
The fresh recriminations came after the Russian Embassy in Britain branded its interactions with the foreign office "utterly unsatisfactory" and said it was "high time" Ambassador Alexander Yakovenko met Johnson to discuss the probe into the poisoning.
"It's Russia's response that has been unsatisfactory," a Foreign Office spokesperson said in a statement, adding it would respond to the request "in due course".
"It's over three weeks since we asked Russia to engage constructively and answer a number of questions relating to the attempted assassinations of Mr Skripal and his daughter.
"Now, after failing in their attempts in the UN and international chemical weapons watchdog this week and with the victims' condition improving, they seem to be pursuing a different diversionary tactic."
Relations between London and Moscow have plumbed new depths following the poisoning of former double agent Sergei Skripal and his daughter Yulia on March 4.
The conditions of the Skripals has continued to improve this week, with the ex-spy no longer in critical condition, the hospital treating him said, and his daughter stating her strength was "growing daily".
Britain and its Western allies have blamed the attack on Moscow, accusing it of targeting the pair with a Soviet-made military-grade nerve agent, known as Novichok.
Russia has vehemently denied any involvement.
The Russian Embassy in London said earlier Saturday Yakovenko had sent a "personal note" to Johnson asking for the meeting.
"We hope that the British side will engage constructively and that such (a) meeting is arranged shortly," a spokesperson added.
The overture comes days after Russia unleashed a blistering war of words against Britain at the UN Security Council over the poisoning, warning it was "playing with fire" and would "be sorry".
Moscow had failed Wednesday in a bid to join a probe into the incident by global chemical watchdog, the Organisation for the Prohibition of Chemical Weapons.
The crisis has led to the biggest wave of tit-for-tat expulsions of diplomats in recent memory.
On Thursday, some 60 American diplomats who were ordered to leave flew out of Moscow, while a day later the US unveiled new sanctions against seven of the country's most influential oligarchs.
Russia promised a "tough response".
A meeting between Johnson and Yakovenko would bring together two of the most vocal players in the drama.
The ambassador held a 90-minute press conference this week in which he denied Russia had ever produced novichok and suggested Britain may be behind the poisoning.
And last month he wrote to a UK policeman hospitalised after exposure to the nerve agent used in Salisbury, insisting on Moscow's innocence and thanking him for his bravery.
Meanwhile Johnson, in one of many public comments on the case, agreed last month with a British lawmaker's assertion that President Vladimir Putin would exploit the 2018 football World Cup in Russia as Adolf Hitler did the 1936 Berlin Olympics.
The charge prompted an angry response from the Kremlin, which branded the comments "disgusting".