Britain and Russia have each expelled four diplomats in a spat over the murder and Moscow's refusal to extradite the chief suspect in the case.

Russia's President Vladimir Putin speaks during his meeting with representatives of youth movements at the presidential country residence in Zavidovo, 120 km (75 miles) north-west of Moscow July 24, 2007. [Reuters]

"What they propose is an obvious vestige of colonial thinking," Putin was shown saying on Russian state television.

"They must have clearly forgotten that Britain is no longer a colonial power, there are no colonies left and, thank God, Russia has never been a British colony," Putin said.

Britain has demanded Moscow extradite Russian businessman Andrei Lugovoy so that he can be put on trial in London for Litvinenko's murder.

Russia has refused, citing its constitution, which forbids the extradition of Russian citizens.

"They should better change their brains than our constitution," Putin said at a meeting with youth organisations in Zavidovo, some 120 km (75 miles) northwest of Moscow.

Shown wearing an open shirt and jeans and sitting surrounded by youth activists, a stern Putin used highly forceful Russian and sometimes seemed angry, almost spitting out the word "brains".

Asked for a reaction to Putin's comments, a Foreign Office spokesman in London told Reuters: "We continue to look for a willingness from the Russian authorities to work constructively with us to bring this crime, committed in the UK, to justice in a British court."

Russia's relations with Britain have been exacerbated by Britain's hosting of anti-Kremlin emigres wanted by Moscow.

They include London-based billionaire businessman Boris Berezovsky, who has accused Putin of being behind the murder. The Kremlin has called those allegations nonsense.

British courts have refused to extradite Berezovsky to Moscow.

"They in London have 30 persons hiding who are wanted by our law enforcement bodies for committing grave and especially serious crimes," Putin said. "But London doesn't give a damn and gives refuge to people accused of committing especially serious crimes.

"And meanwhile they apply tougher standards to the others, including us. This includes handing out recommendations, which I think are insulting to our nation, to amend the constitution."

Putin last week appeared to be playing down what he branded a "mini-crisis" with London saying he hoped the problems could be overcome.