Conservative leader David Cameron has praised former Prime Minister Baroness Thatcher as a "towering figure" during an awards ceremony in London.
He presented the Tory peer, 82, who was PM from 1979 to 1990, with a lifetime achievement award.
Mr Cameron, who has been accused of distancing himself from Lady Thatcher, said she had "transformed our country".
Last year she won praise from Prime Minister Gordon Brown, in a high-profile visit to Downing Street.
Lady Thatcher was being honoured at the Morgan Stanley Great Britons Awards for her "enormous contribution to British life".
Presenting her with the award, Mr Cameron said: "As one of the towering figures of the past 50 years, Baroness Thatcher modernised and transformed our country and once again gave Britain a powerful voice in world affairs.
"She truly is a Great Briton."
He described her as "the greatest peace-time prime minister of the 20th Century" who had rescued Britain "from economic disaster" and dispelled the belief that politicians could only "manage decline gracefully".
Before handing her the award he added: "One of the reasons you deserve this award so much is your enormous courage - courage in sticking to your convictions and always believing they should be followed through."
Lady Thatcher thanked Mr Cameron and urged him on to "a proper majority" at the ceremony at London's Guildhall.
In a statement earlier she said she was honoured to receive the award and it had been a "great privilege" to be prime minister at a time when Britain's economy and "standing on the world stage" had been transformed.
Last September she was invited to Downing Street for talks and a tour of her former home - to the annoyance of some Labour and Tory MPs.
Mr Brown has already courted controversy by referring to Labour's long time foe as a "conviction politician".
But he was praised by one of Lady Thatcher's closest allies, Lord Tebbit, who accused Mr Cameron of being "at great pains to distance himself from her" and of allowing others to call him the "heir to Blair" instead.
Lady Thatcher was prime minister until 1990, when she was ousted by her own MPs.
Officially she withdrew from public speaking in 2002, under doctor's orders following a series of small strokes.