Russia has demanded to know why it has been "denied consular access" to the Skripals in a fresh list of questions for British authorities.
The embassy published a list of 14 questions yesterday over the poisoning of Sergei and Yulia Skripal in Salisbury.
The first question on the list read: "Why has Russia been denied consular access to the two Russian nationals, Sergei and Yulia Skripal, that have become crime victims in the British territory?"
It also included demands to know what treatment the pair were given and queried France's "involvement" in the investigation and asked if the Novichok nerve agent could have been "researched, developed or produced in the UK".
The Russian Embassy previously released a list of 27 questions about the case, including details about the Skripals' condition.
It also claimed Skripal's niece had been inquiring after his health but that she had been ignored by the Foreign Office, and asked why no images or footage of the father and daughter in hospital had been published. Earlier, the UK Foreign Office said it was considering a request from Russia to see Yulia Skripal. She lived in Moscow and was visiting her father.
A spokeswoman for the FCO said the "rights and wishes of Yulia" will be taken into account as well as internal laws.
Yulia Skripal spent three weeks in a critical condition after she and her former spy father were exposed to Novichok on March 4. The Russian Embassy had said it "insists" on the right to see Skripal, 33, after it emerged she was improving rapidly.
An FCO spokeswoman said: "We are considering requests for consular access in line with our obligations under international and domestic law, including the rights and wishes of Yulia Skripal."
Sergei Skripal remains in a critical but stable condition in hospital.
The Russian Embassy also accused British authorities of "another blatant provocation" after an Aeroflot flight was allegedly searched by Border Force officers at Heathrow.
An embassy official suggested that the jet, which had arrived from Moscow on a scheduled return trip, had been searched in connection with the diplomatic crisis over the Salisbury spy poisoning.
The row intensified after the Kremlin ordered Britain to reduce the number of diplomats in Moscow down to the same amount that Russia has in London. In response to reports that more than 50 British diplomats would be removed, the embassy said: "It is not about expulsion of British diplomats, it is about setting the overall number of people working at UK diplomatic missions in Russia and Russian diplomatic missions in the UK on the same level."
The UK expelled 23 Russian diplomats in the wake of the poisoning. Russia has told a number of countries they must send home the same number of diplomats as they had ordered to leave their nations.