Secret diaries, which have lain undiscovered in military archives for more than 80 years, are said to have revealed that the wife of Winston Churchill offered to give one of their children away to family friends who could not conceive.

Clementine Churchill was four months pregnant with her fourth baby when she discussed giving the child to close friend Lady Jean Hamilton, according to this week's The Sunday Telegraph.

The secret came to light in diaries belonging to Lady Hamilton, whose husband, General Sir Ian Hamilton, had fought alongside Winston Churchill on the North West Frontier.

They were discovered by Celia Lee, the wife of John Lee, General Hamilton's biographer, and will be included in a new biography of Lady Hamilton.

Lady Hamilton became a close friend of Clementine Churchill and her diary entry for June 18, 1918, recounts the conversation they had at her London home near Hyde Park.

It reads: "Clemmie asked if I'd like to have her baby; of course I said I would, and asked her when she expected it.

"She said 'in November' and I offered to have her here for it as she had been telling me how expensive a nursing home would be - £25 a week for room alonen - and she said she could not possibly afford it. She said if she had twins I would have one."

Lady Hamilton, who was 57 at the time, had tried in vain for years to have a child.

There is nothing in the diaries to suggest that Clementine, 33, told her husband of the idea and later that year she gave birth to a daughter, Marigold, who they kept but who died of septicaemia three years later.

The Hamiltons subsequently adopted two abandoned babies.

Lady Soames, the Churchills' only surviving child, told the paper: "My mother may have felt at the time that another child was too much of a burden to cope with. My parents were very badly off at this time. She was a born worrier."