OTTAWA—The Canadian government is backing British claims that senior members of Vladimir Putin’s government approved a poison attack against a former Russian spy and his daughter in the U.K. earlier this year.

Canada’s expression of support is contained in a joint statement issued alongside the U.S., Germany and France after British authorities accused two Russian nationals of attempting to kill Sergei Skripal and his daughter, Yulia, in March.

British Prime Minister Theresa May has described the suspects as Russian military intelligence officers and alleged the March attack in Salisbury was approved by senior government officials in Moscow.

Russia has denied any involvement in the attack that used a nerve agent known as Novichok, that also sickened a British police officer and is linked to the death of a British woman who came in contact with the substance.

Canada and its allies say they want Russia to open its Novichok program to the international inspectors.

Britain’s U.N. ambassador is accusing Russia of failing to uphold the ban on using chemical weapons by recklessly using a military-grade nerve agent to try to murder a former Russian spy and playing “dice” with the lives of the people of the southern England town where he lived.

Karen Pierce told the UN Security Council Thursday that the international community must take steps to safeguard people against the use of chemical weapons and “the threat of hostile foreign interference.”

She told reporters that Britain will be discussing next steps with its allies, stressing that the issue goes beyond Salisbury.

“We and our allies will want to think about how we push back on this sort of Russian activity which is not only malign, it’s also reckless,” Pierce said.

She said Britain is calling for the Chemical Weapons Convention and its watchdog agency to be strengthened, for a light to be shone on the use of state agencies to undermine the rule of law, and for sanctions and other measures to be used “to curb threats to our societies.”

The tense back and forth between Russia and the West over the attack in Salisbury is the latest incident in what has become a new Cold War between the two sides in all but name — with no apparent end in sight.