Civil society organisations' contribution to the economy is expected to rise by £25bn in new figures to be published later this month by the Office of National Statistics.

The ONS valued the contribution of “non-profit institutions serving households” to GDP at £37.66bn in 2012, and this is expected to rise to around £63bn, according to preliminary figures released to sector bodies.

The NPISH figure includes the voluntary sector, higher and further education, trade unions and faith groups. However it does not include earned income, so only part of the voluntary sector falls into the NPISH category.

The ONS has been required to make a number of changes to how it values GDP to bring it in line with European Union statistics. This will see activity such as prostitution and drug-dealing, which are legal in other countries, included in GDP.

It will also see changes in other areas such as research and development, meaning its valuation of the economy could grow by over £100bn. However, changes to public sector net debt could increase how much the country owes by £100bn.

Karl Wilding, director of public policy at the NCVO, said the NPISH figures would now be based on data collected in the Civil Society Almanac, which his organisation creates in partnership with the Third Sector Research Centre.

“The important issue for me is that if you’re substantially revising upwards your contribution to the economy, policy makers will take you more seriously,” he said. “The ONS is saying that we’re making a contribution to the economy, rather than costing the country money.”

Wilding said the ONS also produces “satellite accounts” that look at one section of the economy, and he hoped that one would be produced for the voluntary sector.

“The ONS have done some really good work on this,” he said. “They are to be congratulated for taking our sector seriously. I want us to do all that we can to support them to go further.”