Mr Kelin said the Kremlin would publish its proof on the attack “pretty soon”, following Britain’s ambassador to Moscow Deborah Bronnert being summoned to the Russian foreign ministry in connection with the claims.
“We perfectly know about participation of British specialists in training, preparation and execution of plans against the Russian infrastructure and the Russian fleet in the Black Sea. We know that it has been done,” he said.
“It is dangerous. It can bring us to the line of, I would say, no return — return is always possible — but we should avoid escalation.
“This is a warning, actually, that Britain is too deep in this conflict. It means that the situation is becoming more and more dangerous.”
Mr Kelin said Russia was also continuing to investigate the explosions that damaged the Nord Stream 1 and 2 undersea gas pipelines in September. He added that UK special forces had been involved in training the Ukrainians in the use of explosives and undersea drones.
Ukraine war latest — in pictures
In the West, it is widely suspected that the blasts were the work of the Russians themselves in an attempt to increase pressure on European countries with rising energy prices.
A UK government spokesman said the Russian allegations were an attempt to “distract attention” from its illegal invasion of Ukraine and its continuing losses on the battlefield.
“We do not plan to give a running commentary on these allegations; it is no secret that the United Kingdom has taken a public lead in our support to Ukraine — this has been enduring since Russia’s illegal annexation of Crimea in 2014,” the spokesman added.
Earlier, western officials said President Vladimir Putin was likely to come under increasing pressure from nationalist hardliners as he prepares to withdraw Russian forces from the key Ukrainian city of Kherson.
Putin's inner circle — in pictures
Officials said planning to pull forces out of the city on the Dnipro River appeared to be well advanced, with a large proportion of the civilian population having already been moved out.
But while officials expect it to be presented by the Kremlin as a humanitarian evacuation rather than a military retreat, they believe it will not prevent further criticism of the conduct of the war.
“When it does go ahead, we can expect another uptick in pointed criticism of Russian national leadership,” one western official said.
“A key task for us will be to continue to track how this impacts on Putin’s credibility. For now, he appears to continue to successfully deflect with his pointed barbed at his lieutenants.”
The assessment comes as one former Putin ally — the head of the notorious Wagner mercenary group, Yevgeny Prigozhin — stepped up his criticism of the Russian leader.
Military footage shows Ukraine soldiers dismantling Russian flags in a liberated area — video
In a statement earlier this week, he pointedly praised Ukrainian President Volodymyr Zelenskyy — who is routinely denounced by Moscow as a neo-Nazi drug addict — as a “strong and confident leader”.
Officials said that while more troops were arriving in the area in an apparent attempt to shore up their defensive positions, many were recently mobilised reservists who were often “woefully equipped and prepared”.
“In Kherson, it is likely that most echelons of command have now withdrawn across the river, leaving demoralised and leaderless men to face Ukrainian assaults. At least some reservists are arriving in theatre without weapons,” one official said.
Putin says world facing most dangerous decade since Second World War — video
Officials said the Russians were also running “critically short” of munitions, including artillery shells, with additional supplies being sought from North Korea.
“Without the guns and rocket launchers being fired, everything else is grinding to a halt,” one official said.
The move will ban UK service firms offering insurance, brokerage and shipping from being involved in transporting Russian oil unless it is purchased below the cap, which is intended to starve Mr Putin’s administration of cash.