Diana: A memorial garden opened this week in Paris

The items do not include any of the princess's personal effects.

The stables themselves have been converted into a visitor centre in memory of Diana, who was killed in a car accident in Paris in August 1997.

The sale is expected to raise �2m, to be put towards new art works for Althorp and improvements to the Diana memorial centre.

Diana's brother, Earl Spencer, said a shortage of space at Althorp, which has been in the family since 1486, necessitated the sale.

Moving forward

"While it is always difficult to part with objects that have long been associated with my family, our space limitations oblige us to do so."

Earl Spencer is restoring and redecorating Althorp

He said it would help Althorp "to move forward".

"The trustees and I have been working on the restoration and redecoration of Althorp over the past nine years.

"Now that it is close to completion, we are in a position to decide on those objects that are needed at Althorp and those that are definitely surplus to requirements."

He said: "The art collection, in particular, has been stagnant for over a hundred years."

Sotheby's is to issue a catalogue next month.

Memorial garden

About 7,000 children expected to visit Paris garden

The auction announcement comes in the same week that a memorial garden and environmental workshop dedicated to Diana was unveiled in Paris by the city's mayor.

Up to 7,000 children are expected to visit the centre each year to learn about the environment.