Former double agent Sergei Skripal, and his daughter Julia, have been in hospital in a critical condition since March 4.
They were found unconscious on a bench outside a shopping centre in the southern English city of Salisbury.
It's believed they were poisoned by a military-grade nerve agent, and British Prime Minister Theresa May says it's highly likely Russia was involved in the poisoning.
"The government has concluded that it is highly likely that Russia was responsible for the act against Sergei and Julia Skripal. Mr. Speaker, there are therefore only two plausible explanations for what happened in Salisbury on the fourth of March. Either this was a direct act by the Russian state against our country or the Russian government lost control of its potentially catastrophically damaging nerve agent and allowed it to get into the hands of others."
The police officer who attended to the pair, Detective Sergeant Nick Bailey, is also still in hospital, and locals who may have frequented the same restaurant as the Skripals have been warned to wash their clothes.
But Russia isn't happy with Prime Minister May's accusation.
The statement was part of an "information and political campaign based on provocation," according to Russian foreign ministry spokeswoman Maria Zakharova. She also described Prime Minister's questions as "a circus show".
Russian President Vladimir Putin says he won't talk about the poisoning until the UK has finished its investigation.
