The alleged radioactive poisoning of Russian security service defector Alexander Litvinenko, a British national, has strained tensions between London and Moscow. Before his death on November 23, the former agent accused the Kremlin and the president of ordering his murder, a charge that Moscow dismisses.
Speaking on the high-pitched media coverage of the poisoning case, Ambassador Tony Brenton said papers could write whatever they liked.
Brenton said it was premature to make guesses as to who may have put radioactive polonium-210 in Litvinenko's food and who orchestrated the murder, before the outcome of the probe was known.
The diplomat gave assurances that there was no campaign against Russia being waged in the United Kingdom, and expressed his appreciation for Russian authorities' cooperation in the investigation.
The poisoning has triggered heated media debate and parallels to other high-profile assassinations in Russia recently, in particular the murder of another outspoken critic of the Kremlin, journalist Anna Politkovskaya in October.
Foreign Minister Sergei Lavrov condemned Monday attempts to fan the scandal and admitted the affair could damage Russian-British relations.
Scotland Yard detectives are currently working in Moscow as part of the probe.