Prime Minister Tony Blair has paid tribute to former Russian President Boris Yeltsin, who has died aged 76.
Boris Yeltsin played a "vital role" in Russian history, Tony Blair said
Mr Blair was "very saddened" by the death of a "remarkable man" who played a "vital role" in Russian history.
Former Tory prime minister John Major hailed his "tremendous work" in instilling democracy in Russia.
Mr Yeltsin became the first elected president of Russia in 1991, in the dying days of the Soviet Union. He resigned on New Year's Eve 1999.
He died of heart failure in hospital at 1545 (1145 GMT).
In a statement, Mr Blair said: "I was very saddened to learn of the death of former President Yeltsin.
"He was a remarkable man who saw the need for democratic and economic reform and in defending that reform he played a vital role at a crucial time in Russia's history."
President Yeltsin's handling of the privatisation of Russia's state industries has been criticised by some for creating hugely wealthy oligarchs.
"Some say he was too keen to make sure things wouldn't return to communist days," said Sir Malcolm Rifkind, who was Britain's foreign secretary for part of the period that Mr Yeltsin was Russia's president.
Sir Malcolm said his main achievement had been stopping the Communists seizing back control of the Soviet Union in a coup against Mikhail Gorbachev in 1991.
"He was a seminal figure. Yeltsin made a major impact by preventing the coup succeeding, but he also realised that it was necessary to dismantle the Soviet Union."
'Path of reform'
Former prime minister Sir John said Mr Yeltsin, who had a reputation for heavy drinking, had introduced and instilled democracy into Russia.
He told the BBC: "His tremendous work in terms of instilling democracy is what will stand out when people have forgotten the economic difficulties and forgotten the miscellaneous matters about whether he drank too much."
And his predecessor as prime minister, Baroness Thatcher, described him as "a patriot and a liberator".
"Without Boris Yeltsin, Russia would have remained in the grip of Communism and the Baltic States would not be free," she said in a statement.
'Fighter for democracy'
Lord Lamont, who as then chancellor of the exchequer dealt with Mr Yeltsin extensively, described him as "a very brave man, a fighter for democracy, and economic reform".
He said much of the privatisations of the early 1990s had been done under difficult circumstances.
Shadow foreign secretary William Hague said he would always be linked to the creation of democracy in Russia.
A Foreign Office spokeswoman expressed sympathy for Mr Yeltsin's family, adding: "Yeltsin's achievement was to set Russia firmly on the path of reform.
"He never lost his determination that Russia should pursue political and economic transition, despite the difficulties."