Former British prime minister Margaret Thatcher was admitted to hospital today for checks after failing to recover from an infection, reports said.

She was taken to Cromwell Hospital in west London for treatment, the BBC and Press Association newswire reported.

The BBC cited a spokesman as saying her condition was not serious and she was expected to be home in a few days.

Prime Minister David Cameron's Downing Street office had no immediate comment on the reports.

Thatcher was forced to withdraw from a reception there to mark her 85th birthday last week after coming down with flu. She has reportedly failed to recover from the bout of illness.

Cameron hosted the gathering of around 150 friends and former colleagues on Thursday to mark Thatcher's birthday, which had been on the previous day.

She was taken ill with flu on the day of the celebration, so was forced to withdraw -- but insisted the event go ahead without her, according to a government spokesman.

Doctors banned her from public speaking in 2002 following a series of small strokes which aides said left her sometimes confused and with a failing memory.

Her daughter Carol wrote in her 2008 memoir that on her worst days Thatcher struggled to finish sentences and would even forget that her loyal husband, businessman Denis, had died in 2003.

Dubbed the "Iron Lady", Thatcher was prime minister from 1979 to 1990.