The 66-year-old and Yulia, 33, were poisoned with a nerve agent in Salisbury in March and are being kept under armed guard in Britain.
The pair have both refused help from Russia, who are now claiming they are being held against their will.
Russian foreign ministry spokeswoman Maria Zakharova said: "We see it as a murder attempt of Russian citizens and huge political provocations and burden of proof lies with UK side.
"They still refuse to provide consular access saying Yulia does not want to communicate with any Russian representatives while Sergei is a national of UK.
"We would like to see proof that they're refusing and we haven't seen that so far.
"We want to hear them say it to us out loud if they don't want any contact.
"We see it as a forceful containment, that they're being taken by UK state – gross violation of bilateral agreements."
Zakharova also hit out at the UK blaming Russia for the attack, adding the country will be doing all it can to "disentangle the situation" so the process "will be more transparent so the veil cast by UK will be lifted".
Speaking last month for the first time since the attack, Yulia said she is still suffering and vehemently rejected any help from Russia.
She said in her statement: "I find myself in a totally different life than the ordinary one I left just over a month ago, and I am seeking to come to terms with my prospects, whilst also recovering from this attack on me.
"I have specially trained officers available to me, who are helping to take care of me and to explain the investigative processes that are being undertaken.
"I have access to friends and family, and I have been made aware of my specific contacts at the Russian Embassy who have kindly offered me their assistance in any way they can.
"At the moment I do not wish to avail myself of their services, but, if I change my mind I know how to contact them."
Tensions between Russia and the UK still remain high following the attack, which left Yulia and her dad fighting for their lives in Salisbury District Hospital.
The Wiltshire town was cordoned off for weeks as police investigated, with fears "hot spots" of Novichok could remain.
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