Drugs and prostitution contributed almost £10bn to the economy in 2009

Prostitution was estimated to be worth £5.3bn to the UK economy in 2009. Photograph: Alex Segre/REX Photograph: Alex Segre/REX

Illegal drugs and prostitution contributed almost £10bn to the UK economy in 2009, according to newly released figures from the Office for National Statistics (ONS).

The statistical authority is currently revising how it makes its calculations for the UK's national accounts - which is used to provide Britain's Gross Domestic product (GDP).

As well as the inclusion of household expenditure on new cars (which has a negligible impact in case you're interested), the stats now include "illegal activities" such as drugs and prostitution.

Using 2009 as a reference year the ONS calculated the following figures:

That's just under £0.83bn from cannabis and £3.6bn from other drugs - together worth £4.4bn to Britain's GDP that year.

Prostitution was worth more though at £5.3bn, which means illegal activities as a whole were worth about £10bn to the UK economy in 2009.

The ONS estimates that this £10bn could have been worth somewhere in the range of £7bn to £11bn in the years between 1997 and 2009.

What does that all mean to the UK's economy as a whole? In 2009, the ONS estimates that these illegal activities would have increased the UK's GDP by 0.7%. The changes as a whole would have added around £33bn - or 2.3%.