Britain expelled 23 Russian diplomats over the nerve agent poisoning of a former spy, and suspended high-level contacts, including for the world cup, as the US joined it in blasting Moscow at the UN.

British Prime Minister Theresa May told parliament that Russia had failed to respond to her demand for an explanation on how a Soviet-designed chemical, Novichok, was used in the English city of Salisbury on March 4.

At an emergency meeting of the UN Security Council in New York, US sided firmly with Britain, rejecting Moscow’s claim that it was not involved in the attack on Sergei Skripal and his daughter.

The White House also issued a statement that the US “stands in solidarity with its closest ally”.

NATO allies have expressed their support for Britain following the first use of a nerve agent in Europe since World War II.