Margaret Thatcher once said she owed nothing to feminism, but the only woman ever to become British prime minister unwittingly cleared the way for other women to succeed in the male-dominated world of politics, observers said on Tuesday.

In the impassioned debate sparked by her death on Monday, Thatcher's role as a pioneer for women in politics is among the thorniest subjects.

In a glowing tribute in which he described her as a "true friend" of the United States, President Barack Obama said she was an example to girls that "there is no glass ceiling that can't be shattered."

Australian Prime Minister Julia Gillard said Tuesday that Thatcher "was a woman who changed history for women".

Yet in 11 years in office, Thatcher only appointed one woman to any of her cabinets, elevating Janet Young to leader of parliament's upper House of Lords.

Gisela Stuart, a senior current Labour lawmaker, said whether she recognised it or not, Thatcher "broke that ceiling -- she actually said that there is no place where a woman cannot go and succeed.

"While you can accuse her that she didn't bring women in with her, she broke down the doors and it was then up to the next generation of women to walk through those doors," Stuart told AFP.

There were around 40 women MPs in parliament's lower House of Commons when Thatcher reluctantly left power in 1990. Today 146 of the 650 lawmakers are women.

Though Stuart is from the other side of the political divide to Thatcher and the Conservatives, she said it is often overlooked that the former prime minister also took on the macho world of trade unions.

"The left likes to forget that you have to go a long way to find something more chauvinistic than the brotherhood in the trade unions. She broke their power," she said.

Beatrix Campbell, a feminist writer and author of "The Iron Ladies: Why Do Women Vote Tory?", said: "The remarkable thing about Margaret Thatcher was the way that she performed power not in a sense to say to women you can be like me but, 'I am the exception'.

"Thatcher hated feminism. It's an egalitarian project, and she was an elitist -- never an egalitarian," Campbell said in a BBC radio debate.

Thatcher never hid her contempt for feminist militants, saying: "I owe nothing to women's lib."

And she once commented that "I hate those strident tones we hear from some women's libbers."

At the same time, Thatcher, a married mother of two children, had no qualms about praising a women's supposed advantages over men.

"If you want something said, ask a man. If you want something done, ask a woman," was one of her best-known quotes.

Margot James, a current Conservative lawmaker and the party's first openly lesbian MP, was in her 20s when Thatcher came to power.

She said it was unfair to blame Thatcher for having so few women in her cabinet, because at that time there were not many women MPs to choose from.

"She had limited room for manoeuvre in that respect. What she did was that she showed women that they could reach the very top in any field," she said in the debate with Campbell.

"She democratised Britain in so many senses. She opened up the economy, and gave opportunities to all, regardless of gender."

Douglas Hurd, who served as foreign minister under Thatcher, also dismissed suggestions that as a woman herself if was her job to promote women.

"That wasn't her job, for heaven's sake," he said. "She wanted to appoint the best people."