"This could be in the interests of the British government which found itself in an uncomfortable situation having failed to fulfill promises to its electorate about the conditions for Brexit," Lavrov said at a press conference in Moscow on Monday, referring to Britain's planned departure from the European Union.
The Russian diplomat stressed that "leaders of a whole number of countries" are questioning Britain's account of the crime, saying, "Britain will not manage to evade answering these questions. Because they are already only too obvious and it's only too obvious that our British colleagues have lost their sense of reality."
Ties between Moscow and London hit a new low after Britain last month accused Russia of poisoning Sergei Skripal and his daughter, Yulia, without offering any proof.
Russia has denied any involvement in the incident, which occurred on March 4 in the British city of Salisbury. The Skripals are being treated in a UK hospital.
The UK claims the nerve agent allegedly used in the poisoning was Novichok, which was developed in the former Soviet Union, basing its accusations against Moscow on that assertion.
Moscow says the substance could have originated in the countries studying Novichok, including the UK itself, Slovakia, the Czech Republic, and Sweden.
During the Monday press conference, Lavrov accused Western countries of "playing children's games" and said there were “other explanations” as to who may have carried out the attack on the former Russian spy.
"There are other explanations besides those put forward by our Western colleagues who declare that it can only be the Russians who are responsible," he said.
"Experts say that it could be highly advantageous to the British security services as well, who are well known for their capacity to act with a license to kill,” Lavrov added.
The Russian foreign minister also complained that British authorities had declined to give consular access to the Skripals, and that the situation had not changed despite Yulia Skripal's improved condition following medical treatments.
Earlier in the day, the Russian embassy had accused Britain of breaching diplomatic convention by blocking access to the 66-year-old ex-double agent and barring Moscow from doing investigation into the matter.
"28 days passed since the poisoning of Sergei & Yulia Skripal. UK hasn't complied with its obligation under the consular convention to provide access to the Russian citizens and the course of investigation," the mission said in a tweet.
Following the poisoning incident, Britain expelled 23 Russian diplomats and their families, prompting Russia to send back as many British diplomatic personnel.
Nearly 30 nations have so far expelled Russian envoys over the poisoning, despite the failure by the UK to provide any evidence and Russia’s denials.
NATO has also expelled seven diplomats from Russia’s mission to the Western military alliance.
Moscow primarily warned against an escalation but later proceeded to expel foreign diplomats in accordance with its policy of reciprocation.
On Friday, Russia expelled 59 diplomats from 23 countries and said it reserved the right to take action against four other nations as part of tit-for-tat measures.
The diplomatic tensions are unprecedented since the Cold War.
