Research from law firm Pannone has found that assets from deceased people with no named beneficiaries – known as intestacies – in England and Wales totalled £38.5m in 2011/12, a rise of 91% on the year before.

Pannone believes that the majority of these ownerless assets – known as ‘bona vacantia’ – were smaller estates, rather than being made up of higher value intestacies.

Pannone’s Liz Braude said: “There is no clear explanation, thought, as to why the amount of bona vacantia has risen by so much in such a relatively short space of time.

“One must presume that some cases of this nature involve people who felt that their assets were so comparatively small that it wasn’t necessary to make a will.

“There is also a risk if, in having made a will, it isn’t kept up-to-date, that beneficiaries and executors don’t know where it is, or any intended heirs do not survive the person making it.”

Figures from the Legal Services Commission have previously suggested that more than one in six Britons die intestate, with the value of their assets going to the Treasury on behalf of the Crown.

But estates which fall within the boundaries of the duchies of Lancaster and Cornwall, which provide income for the Queen and the Prince of Wales respectively, will go to those duchies.

Pannone found that income due to the Duchy of Lancaster from ownerless estates rose from £3.15m in March 2011 to £3.35m in March 2012. The income due to the Duchy of Cornwall meanwhile rose from £75,000 to £552,000 in the same period.

Intestate money going to the Treasury almost doubled, with £33.5million swelling its coffers in 2012 compared to £17m the year before.

Efforts are made when estates are left without wills or heirs to track down relatives who may be entitled to the assets.

And enquiries to the Treasury about unclaimed assets did increase by 6.4% in 2011/12, with some 28,170 queries handled by the department during the 12 months.