MPs and peers held a minute's silence in memory of George Floyd, the black man whose death in US police custody has sparked a global wave of protests.
The House of Commons and Lords chambers, as well as virtual committee hearings, fell silent at 11am on Tuesday.
Since Mr Floyd's killing on 25 May, protests have been held across the UK.
Prime Minister Boris Johnson has urged people to "work peacefully, lawfully" to defeat racism and discrimination.
Mr Johnson was chairing a cabinet meeting in Downing Street as the silence was being marked in Parliament.
Asked if ministers had taken part in the silence, the PM's spokesman said it happened around the time they were discussing the "anger and the grief that is not just felt in the US but around the world including the UK following the death of George Floyd".
The prime minister had said "those who lead and govern simply cannot ignore the depth of emotion that has been triggered" and there was an "undeniable feeling of injustice" among black and ethnic minority groups, his spokesman said.
"The PM said we're a much, much less racist society than we were but we must also frankly acknowledge that there's so much more to do in eradicating prejudice and creating opportunity," his spokesman added.
The PM also stressed that those who break social distancing or attack public property or police "will face the full force of the law".
Writing on Twitter the Labour party leader Sir Keir Starmer said George Floyd "must not become just another name. His death must be a catalyst for change".
He later tweeted a picture of himself and his deputy, Angela Rayner, kneeling in a pose popularised by anti-racism campaigner and American football player Colin Kaepernick.
On Monday, Home Secretary Priti Patel told MPs that, while most demonstrators acted peacefully, "justice will follow" for any who engaged in violence.
Mr Floyd died after a Minneapolis police officer kneeled on his neck for over eight minutes.