Former prime minister Margaret Thatcher, 83, is to have an operation on her upper arm after breaking it in a fall last week, her spokesman said today.

She will stay in London's Chelsea and Westminster Hospital for several more days after the operation, which is scheduled for Friday, her private secretary Mark Worthington said.

"Lady Thatcher is to undergo a routine surgical procedure to insert a pin into the bone of her upper arm in order to assist the healing process. Therefore she will be remaining in hospital for the time being."

Thatcher, Britain's first woman prime minister, was taken to hospital six days ago after breaking her arm in a fall at her London home.

Her son, Mark, told reporters outside the hospital today that she was "very well" and Worthington said she was in good spirits.

Thatcher has had intermittent health scares since she was forced from power by her own Conservative Party in 1990.

She suffered a series of mild strokes in late 2001 and 2002 and cancelled several engagements a few months later due to an undisclosed illness. On the advice of her doctors, she cancelled her public speaking schedule and cut back personal appearances.

Thatcher's daughter Carol revealed in 2008 that her mother had been suffering from dementia for several years and often struggled to remember things -- including that her husband Denis had died in 2003.

One of her most recent public engagements was a meeting with Pope Benedict in Rome last month.