But Prime Minister Gordon Brown said Britain will make "no apologies" for expelling the four Russians.
Mr Brown said that because "there is no forthcoming co-operation, then action has to be taken".
The Foreign Office has not named the four Russian diplomats, but the BBC understands they are intelligence officers.
'Absolutely clear'
Recources said that an equivalent Russian response to the expulsions is widely expected.
Mr Litvinenko, another former KGB agent, died of exposure to radioactive polonium-210 in London in November 2006.
The radioactive isotope used to poison Mr Litvinenko was found in several places that Mr Lugovoi had visited in London.
But Mr Lugovoi told Russian television that the outcome of the inquiry had been predetermined.
He said: "The British authorities have in effect emphasised yet again that the Litvinenko case actually has a political subtext.
"In all the eight months that this row has been developing in earnest, I have not received a single official invitation from the official British authorities, and all those statements that the investigation was carried out competently are lies."
On a visit to Berlin on Monday, Mr Brown said: "When a murder takes place, when a number of innocent civilians were put at risk as a result of that murder, and when an independent prosecuting authority makes it absolutely clear what is in the interests of justice, and there is no forthcoming co-operation, then action has to be taken."
The prime minister added that he wanted a "good relationship" with Russia.
Russia's Foreign Ministry chief spokesman Mikhail Kamynin said: "London's position is immoral.
"Such provocative actions masterminded by the British authorities will not be left without an answer and cannot but entail the most serious consequences for Russian-British relations".
Russian President Vladimir Putin's spokesman Dmitri Peskov said: "We don't want to be provoked into a ping-pong game, although of course the Russian side will provide a necessary response."
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