A survey of Britain's 50 most powerful women has concluded that women are still being forced to choose between motherhood and career.

"At least a third of the women are childless, while almost all of their male counterparts are fathers," said Management Today magazine (MT).

And there has been a 50% turnover in women winning a mention since the list was last drawn up two years ago.

MT drew up the list of high-fliers after canvassing head-hunters, economists and influential figures in the City of London.

'Pushing barriers'

Marjorie Scardino, chief executive of Pearson, the media giant which owns Penguin Books and the Financial Times, holds on to her place at the top of the list.

Ms Scardino also remains the only woman at the helm of a FTSE 100-listed company.

The British prime minister's wife Cherie Blair is ranked as the country's second most powerful woman.

One of the youngest barristers to become a Queens Counsel and earning more than �250,000 a year, she manages to successfully combine work and family life.

Marjorie Scardino: Still most powerful woman

Many of the women chosen are "pushing the barriers of traditional male bastions," said Rufus Olins, editor in chief of MT.

But there have been a lot of changes in the top 10.

There were four new arrivals in the top 10, including Clara Furse, boss of the London Stock Exchange, and Kate Barker, one of the two women members of the Bank of England's interest rate setting committee.

Her colleague, Marian Bell, also gets in for the first time, at number 13.

Dotcoms fall

The report welcomes the high turnover, saying "it illustrates that the number of talented women at the top is growing".

"This level of turnover demonstrates that the pool from which the list is drawn is getting deeper and the quality of the swimmers is rising," said report author Richard Reeves.

Changes in the economy are reflected too. Dot.com boom entrepreneur Martha Lane Fox, who co-founded lastminute.com, has slipped to 50th from fifth in 2000.

Although the overwhelming majority of women on the list come from the world of business, it also includes writers and cultural figures.

Harry Potter author J K Rowling appears for the first time, at number 36, while TV cook Delia Smith falls to 39 from 20th.