Her father Sir Reginald Sheffield has a property portfolio worth upwards of £20 million, a £5 million stately home near York, a house in London and Normanby Hall, the family seat in Lincolnshire.
In another interview, when Mr Cameron was asked about property that he and Samantha owned, he said his wife didn't own any properties but "owns a field in Scunthorpe".
He was thought to be referring to several thousand arable acres in North Lincolnshire belonging to Samantha's wider family. Farmland in the area is worth more than £5,000 an acre.
Samantha, who received a £400,000 windfall from the sale of her stake in the luxury stationery group Smythson when it was sold in 2005, also owns a £77,000 stake in her father's Normanby Estate Holdings.
Her mother Annabel runs the successful furniture and interior retailer, Oka. When she divorced Sir Reginald, she married another wealthy aristocrat, William Astor, who owns an 18,000-acre estate on the Scottish island of Jura.
Mr Cameron's ancestors, while not as wealthy as his wife's, were also prosperous: his great-great-grandfather, Emile Levita, who was brought up in a family of Sephardic Jews, became a director of the Chartered Bank of India, Australia and China, owned a grouse moor in Wales, and started the family traditions of making money in the City and sending sons to Eton.
The Cameron family's inheritance tax planning is not the first time his adept financial management has come under the microscope.
In 2009, The Mail on Sunday revealed that he had paid off the £75,000 mortgage on his London home after taking out a £350,000 HSBC mortgage on his Oxfordshire home - which he then claimed for under MPs' expenses.
Mr Cameron said he had paid off the mortgage by "selling shares" - but if he had put the share proceeds towards the constituency home it would have reduced the bill for the taxpayer.
The value of the couple's London property has also been boosted by a basement conversion at a cost of more than £250,000.
