"They are making proposals to change our constitution which are insulting for our nation and our people," Putin said in televised remarks during a meeting with activists of pro-Kremlin youth organizations. "It's their brains, not our constitution, which need to be changed. What they are offering to us is a clear remnant of colonial thinking."
Prime Minister Gordon Brown's office had no immediate comment on Putin's remarks.
Putin's statement comes amid an escalating war of words between Moscow and London over Russia's refusal to extradite former KGB officer Andrei Lugovoi, the sole suspect in the poisoning death of Litvinenko. Lugovoi, one of three Russians who met with Litvinenko in a London hotel Nov. 1, the day he fell ill after ingesting radioactive polonium-210.
The standoff escalated last week after Britain responded to Russia's refusal to extradite Lugovoi by announcing the expulsion of four Russian diplomats. Russia countered by announcing that it will expel four British diplomats.
Russia said Lugovoi could not be extradited because its constitution forbids it, but Britain's ambassador Sir Anthony Brenton challenged that argument in an interview published Monday and said Russia could get around the ban if it wanted to cooperate in the case.
Putin said the British proposal to change the constitution showed that British officials were still thinking in terms of the British Empire.
"They forgot that Britain is no longer a colonial power," he said. "They insult themselves by giving such advice, showing that they are thinking in terms of the last or even previous century."
Litvinenko, a renegade former member of the Russian secret services hated by many former colleagues, died in a London hospital in November. He accused President Vladimir Putin on his deathbed of being behind his poisoning - charges the Kremlin has angrily denied.