"Now our Western partners, I mean primarily the United Kingdom, the United States and several countries that have blindly followed them, have run out of niceties, resorting to open lies, to outright misinformation. We will respond to this fairly calmly, coolly, and insist that any accusations, any allegations must be justified by facts”.

Mr Lavrov’s remarks follow the publication on Sunday of a letter containing 13 questions that the Kremlin has sent the Organisation for the Prohibition of Chemical Weapons (OPCW) regarding what it called the “fabricated Skripal case”.

In it the Russian government demands to know what kind of assistance the UK has requested from the OPCW, what evidence investigators have so far collected, in which laboratories tests are being carried out, the methods used, and who has access to any samples throughout the process.

"There are many questions, and the inability of our UK colleagues to answer them will mean only one thing — that this is all a fiction, and more specifically, a gross provocation," Mr Lavrov added.

"We have strictly distributed specific questions in full compliance with the Convention on the Prohibition of Chemical Weapons. The questions are addressed to the technical secretariat of the OPCW, and to our British colleagues and to our French colleagues, because suddenly some reports have appeared and President Macron had said that France was actively involved in the investigation.”