Britain pointed a finger at Russian President Vladimir Putin on Thursday over an attack by nervous agents on a former Russian spy in England, an accusation that Moscow rejected as "unacceptable."
London accused two members of Russian military intelligence of using Novichok to try to kill former Russian double agent Sergei Skripal and his daughter Yulia in March.
Security Minister Ben Wallace said Putin was "ultimately" responsible for the poisoning in the city of Salisbury, in the south-west of the country, prompting an angry response from Moscow.
"For us, any kind of accusation regarding the Russian leadership is unacceptable," Kremlin spokesman Dmitry Peskov told reporters.
Britain has previously accused Russia of orchestrating the attack, but Moscow denies any involvement and insists that it is ready to cooperate in any investigation.
"Neither the top leadership of Russia nor those in the lower categories, nor any official representative have anything to do with the events in Salisbury," said Peskov.
London and its allies expelled dozens of Russian diplomats after the poisoning, prompting an eye-to-heart response from Moscow and plunging relations into a new low.
In an important new development, Prime Minister Theresa May announced on Wednesday that the police had issued international arrest warrants for the two suspects, identified as Alexander Petrov and Ruslan Boshirov.
He said they were members of Russian military intelligence and that they obeyed "high-level" orders, but Wallace went further when asked if Putin had responsibility.
"In the end he does it to the extent that he is the president of the Russian Federation and it is his government that controls, finances and directs military intelligence, the GRU, through his defense ministry," Wallace told radio of the BBC.
He added: "I do not think anyone can say that Mr. Putin is not in control of his state … And the GRU is, no doubt, not rogue.
"It is directed, linked to the high offices of the Russian General Staff and the defense minister, and then to the Kremlin and the president's office."
Britain will report to the UN Security Council later on Thursday on its latest findings, and the meeting will begin at 11:30 a.m. (1530 GMT).
Support from allies
The United States ambassador to London, Woody Johnson, and the Australian government have offered support for Britain's stand against Russia.
Wallace said his government will seek to "keep up the pressure" on Russia "to say that the behavior we have seen is totally unacceptable."
The options include "more sanctions: obviously, we are taking it to the UN to present our case," he said.
The United States imposed new sanctions on Russia after the Salisbury attack.
Meanwhile, Britain is looking to work with EU allies on a sanctions regime related to the use of chemical weapons, officials said.
Amid reports that Britain was planning a direct response in cyberspace, Wallace said the Russians were the main operators behind the attacks on British networks.
"We retaliate on our way … within the rule of law and in a sophisticated way, so they know the cost of what they do," he said.
The government is also reviewing visa applications from rich Russians in Britain, and is preparing new powers to stop people on the border if "malign state activity" is suspected.
The Skripals survived the poisoning but a local man, Charlie Rowley, picked up a bottle of fake perfume that contained Novichok weeks later.
Rowley gave it to his girlfriend, Dawn Sturgess, who later died.
British prosecutors accuse Petrov and Boshirov of conspiracy to murder Skripal, attempted murder and the use of a banned chemical weapon.
They said they would not formally demand their extradition, since Russia does not extradite its citizens, but they have obtained a European arrest warrant for the couple.