RUSSIA has refused to respond to Theresa May’s ultimatum over the attempted murder of Sergei Skripal and his daughter Yulia.

On Monday, the Prime Minister had told Russia they needed to account for how a Soviet nerve agent known as Novichok could have been deployed in Salisbury.

READ MORE: Rex Tillerson fired for not ‘thinking the same’ as Donald Trump on Iran

Yesterday, in an ominous warning, the Russian foreign ministry’s spokesman told May it was unwise to “threaten a nuclear power”.

However, after what seemed to be a reluctance on the behalf of the White House to get involved, President Donald Trump told May in a phone call that the US was “with the UK all the way”.

In a series of tweets, the Russian Embassy in the UK spelled out why they were refusing to respond: “Moscow will not respond to London’s ultimatum until it receives samples of the chemical substance to which the UK investigators are referring.

“Britain must comply with the Chemical Weapons Convention which stipulates joint investigation into the incident, for which Moscow is ready.

“Without that, there can be no sense in any statements from London. The incident appears to be yet another crooked attempt by the UK authorities to discredit Russia.

“Any threat to take ‘punitive’ measures against Russia will meet with a response. The British side should be aware of that.”

Britain’s ambassador to Russia was summoned by Moscow and told by first deputy foreign minister Vladimir Titov that the Kremlin “strongly protested” the accusations, the embassy said.

Skripal, 66, was found along with his daughter, Yulia, on a bench in The Maltings shopping centre in Salisbury last week. They remain in a critical but stable condition.

May is due to set out how the UK will respond in the Commons today.

It looks increasingly likely one response will be for the Kremlin-backed television channel RT to be taken off air.

Ofcom said that evidence of the Russian state acting unlawfully would mean it may no longer be deemed “fit and proper” to hold a broadcasting licence.

Ofcom said in a statement: “As the independent UK broadcasting regulator, Ofcom has an ongoing duty to be satisfied that broadcast licensees remain fit and proper to hold their licences.

“We have today written to ANO TV Novosti, holder of RT’s UK broadcast licences, which is financed from the budget of the Russian Federation.

“This letter explained that, should the UK investigating authorities determine that there was an unlawful use of force by the Russian State against the UK, we would consider this relevant to our ongoing duty to be satisfied that RT is fit and proper.

“The letter to RT said that we would carry out our independent fit and proper assessment on an expedited basis, and we would write to RT again shortly setting out details of our process.”

RT said it disagreed with Ofcom’s position, adding it was “conflating its role as a broadcasting regulator with matters of state”.

The station broadcasts a show by former Scottish First Minister Alex Salmond.

RT said in a statement: “We disagree with the position taken by Ofcom; our broadcasting has in no way changed this week from any other week and continues to adhere to all standards.

“By linking RT to unrelated matters, Ofcom is conflating its role as a broadcasting regulator with matters of state.

“RT remains a valuable voice in the UK news landscape, covering vital yet neglected stories and voices, including those of the many MPs and other UK public figures who have been shut out of public discourse by the mainstream media.”