Britain today acknowledged the Russian presidential elections had delivered "a decisive result" in favour of Vladimir Putin.
Downing Street said that while there had been "some problems" with the election, the overall outcome was not in doubt.
David Cameron is now expected to call Mr Putin later today. The Prime Minister's official spokesman said they would discuss "a number of issues".
Mr Putin last night claimed victory with more than 60% of the vote, despite opposition claims of widespread vote rigging and electoral fraud.
However, Mr Cameron's spokesmen said even independent assessments of the count had put Mr Putin clearly ahead.
"It is clear that the election has delivered a decisive result," the spokesman said.
"Even the NGO (non-governmental organisation) polling data put Putin above the 50% needed to win in the first round.
"It is right that these assessments have taken place. They have clearly identified some problems. We would like to see these issues addressed over time."
An observer mission from the Organisation for Security and Co-operation in Europe concluded there were "serious problems" in the way the election was conducted.
The head of the mission, Tonino Picula, said: "There was no real competition, and abuse of government resources ensured that the ultimate winner of the election was never in doubt."
Mr Putin's return to the Kremlin marks his third term as president following a single term as prime minister.
Police are braced for public disorder once the vote closes following unprecedented mass protests over Mr Putin's system of so-called "managed democracy".