Russian President Vladimir Putin has suggested Moscow will regard this as a serious escalation of the war which equates to “direct participation” of Nato countries.
“If that is the case, we will take corresponding decisions based on the threats that will be created to us,” he said on state TV.
Former national security advisor Lord Peter Ricketts said the withdrawal of diplomatic accreditation was a retaliatory punishment for the upcoming meeting in Washington and the UK’s continued military support of Ukraine.
“The timing is too coincidental,” he told Radio 4’s Today programme, describing the allegations levelled at the six diplomats as “trumped up”.
Lord Ricketts said he was not surprised President Putin took the opportunity to “strike first” in a move to try and “intimidate western politicians”.
Announcing the decision, the FSB said the diplomats had shown signs of conducting intelligence and were tasked with inflicting a “strategic defeat on our country”.
In a Telegram post, Russian foreign ministry spokeswoman Maria Zakharova said Moscow “fully share the assessments” made by the FSB on the activities of the diplomats.
An FSB officer told Russian media “hints” to “stop this practice [of gathering intelligence]”, were not heeded.
The security service added that it would revoke accreditation from more British diplomats if they are found to be involved in similar activity.