The ambassador said this in an interview with Izvestia.
Kelin, commenting on the possible supply of shells with depleted uranium by London, stressed that the long-term consequences for Ukraine and its inhabitants are of no interest to the British authorities.
The ambassador recalled that the Russian side has repeatedly pointed out London's violation of the principles of international law.
"All crimes, including the supply of prohibited weapons, are recorded. We will not leave them unanswered," he stressed.
Earlier, the Russian Foreign Ministry said that Britain's decision to supply Ukraine with ammunition with depleted uranium will not remain without Russia's response.
Russian President Vladimir Putin also said that Russia will be forced to react if the collective West begins to supply Ukraine with weapons with a nuclear component.