The government wants to realise up to £5bn in corporate asset sales by March 2020, including looking to “develop options to bring private capital into the Ordnance Survey before 2020” (page 74).

Prospect negotiator Ben Middleton, speaking on behalf of OS specialists, said: “This announcement is a cause for concern becomes it comes so soon after the transition to a government-owned company (GovCo) in April 2015.

"Clear assurances were given that becoming a GovCo would not change the ownership of Ordnance Survey and that it would remain in public ownership.

“Prospect is not ‘anti-private sector’, and private investment into Ordnance Survey could be a positive move if it is done in a way that is compatible with the existing GovCo strategy. This was to look at further partnering arrangements to enable OS to move into new markets and develop new products and services.

“We want Ordnance Survey to continue to be a successful organisation. But we are quite clear that we want it to continue as a 100% publicly-owned body fulfilling its public task as the National Mapping Agency.

“Investment in the form of equity share or partial sell-off, where profit would increasingly come before public service, would be contrary to that policy position.

“We do not believe that maintaining a majority ownership or ‘golden share’ provides any meaningful assurance that wholesale privatisation would not follow.

“Look at the British Airports Authority or more recently Royal Mail – such assurances are effectively meaningless in the longer term.

"The chancellor’s statement also proposed exploring options to sell-off the government’s remaining 49% stake in National Air Traffic Services (NATS), previously protected by so-called ‘golden share’ assurances.

“Privatisation, whether whole or in part, would raise doubts over the long-term viability of important aspects of the organisation’s activities.

"It would also increase the risk of higher costs for local and national government and/or a decrease in the quality and currency of data.

“Rural area mapping might be considered of little economic value, but such activities are vital in the context of emergency relief – think of the foot and mouth outbreak or emergency flood relief for example.

“Ordnance Survey holds a position of national strategic importance and we must ensure it continues to do so. Public ownership is key to that.

“We have a good working relationship with Ordnance Survey and expect that to continue. It is clear that further consultation is required to understand precisely what is envisaged by the Chancellor’s statement.

“Prospect will be will be seeking meetings with Ordnance Survey, the government and the Shareholder Executive to establish that meaningful consultation takes place on any proposals.

“Branch officials have also been developing links with the ‘We Own It’ organisation  as part of their ‘Top Trumps’ campaign.

"We will continue to work closely with them and other relevant organisations in seeking to ensure that Ordnance Survey continues to be held in public ownership for the public good.”