Russia’s Embassy to the United Kingdom has issued a scathing tweet after Prime Minister Theresa May took retaliatory action over the poisoning of a secret agent on British soil.

On Thursday the embassy tweeted an image of a thermometer against a backdrop of ice – a reference to the Cold War – in a response to the expulsion of 23 Russian diplomats from the UK.

“The temperature of UK/Russia relations drops to -23, but we are not afraid of cold weather,” the tweet read.

Ms May expelled the diplomats, who she described as “undeclared intelligence officers”, after accusing Russia of being responsible for a nerve gas attack on ex-Russian spy Sergei Skripal and his daughter Yulia on March 4 in Salisbury, south of England.

The temperature of 🇷🇺 🇬🇧 relations drops to ➖2️⃣3️⃣, but we are not afraid of cold weather. pic.twitter.com/mand9YyoaE

— Russian Embassy, UK (@RussianEmbassy) March 14, 2018

In several previous tweets, the Russian embassy said it would refuse to cooperate with the UK inquiry into the Salisbury spy poisoning until it received a sample of the nerve agent that was used in the attack.

Alexey Muraviev, an associate professor of national security and strategic studies at Curtin University, said the tweet suggested a “return to the Cold War”.

“It means the relations between London and Moscow have now reached sub-zero temperatures. We’re not talking about a temporary chill, but an ice age,” associate professor Muraviev said.

Associate professor Muraviev said the embassy’s latest tweet exemplifies Anglo-Russian relations sinking to its lowest point since the Cold War.

“The Russians tend to showcase their dark humour in times of crisis,” he said.

“The relations between London and Moscow were very frosty throughout the 1990s and in the 2000s.

“There were several spy scandals that robbed this relationship but obviously not to the point or to the magnitude of what were seeing just now,” associate professor Muraviev said.

Professor Mark Edele, from the University of Melbourne’s School of Historical and Philosophical Studies, said the tweet was “relatively harmless” and would not “make a very bad relationship worse”.

“They’re basically saying our relationships are at a new frosty low but we don’t mind, we’re tough Russians, we can deal with that,” Professor Edele said.

Professor Edele said there may be a retaliation from Russia for Ms May’s expulsion of the diplomats.

“They will likely expel British diplomats in response because they’re saying they’ve been punished for something they didn’t do … as odd as that might sound.

“They act as if they’ve been victimised.

“I think the diplomatic relations will go further downhill before they get better,” Professor Edele said.

He said he is not particularly worried about the tweet.

“I’m more worried by two nuclear powers increasingly getting at loggerheads and potentially having no diplomatic relations at all.

“That’s the worry,” professor Edele said.