The death of Alexei Navalny is expected to be discussed by MPs later, as Commons returns after recess.
The Government is currently weighing up its response to the death of the jailed opposition leader, as Western capitals heaped blame on Vladimir Putin.
Foreign Secretary Lord Cameron has already signalled that there could be fresh sanctions against Russia officials, amid questions for the Russian authorities over how exactly Mr Navalny died.
The row over his death comes as Ukraine and its allies prepare to mark the two-year anniversary of the Russian invasion.
Shadow foreign secretary David Lammy told the BBC on Sunday Labour would try to “plug” gaps in the current sanctions regime if it wins power.
Mr Navalny’s team said on Saturday that the politician was murdered and accused authorities of deliberately stalling the release of the body.
His mother and lawyers received contradictory information from various institutions they visited in their quest to retrieve the body.
It remains unclear what response the Government and other allies may take against Mr Putin, with Moscow already facing heavy sanctions since the start of the war in Ukraine.
The UK has backed using seized Russian central bank assets currently held in the West as one way of financing the reconstruction of Ukraine.
Prime Minister Rishi Sunak spoke to European Commission president Ursula von der Leyen on Sunday, with the death of Mr Navalny raised in the conversation alongside aid for Ukraine.
A Downing Street spokeswoman said the pair “underscored the importance of providing continuing support to the Ukrainian people”.
She said: “The Prime Minister welcomed the recent announcement that the EU will provide 50 billion euro support to Ukraine, and outlined the work the UK is doing through our security cooperation agreement.
“The Prime Minister and President Von der Leyen expressed their outrage at the death of Alexei Navalny, and underscored the utmost importance of holding those responsible within the Russian system to account.”
It comes as Ukrainian President Volodymyr Zelensky struggles to convince Republicans in Washington to facilitate a major funding package for Kyiv.
Lord Cameron has urged lawmakers to pass the 60 billion dollars (£47.6 billion) package.