A publicly-owned airport has been controversially sold for less than half its estimated £21 million value.

Shoreham airport has been sold on a 150-year lease for £8.6 million in a deal which campaigners fear will pave the way for proposed major expansion.

Joint owners Worthing Borough Council and Brighton and Hove City Council accepted the bid by their preferred contractor The Erinaceous Group.

The figure paid for the historic 248 acre, three-runway airport, was substantially less than the figure suggested by the district auditor who, after a check of the councils' accounts in November last year, found its real value was more than £21 million.

Campaigners, councillors and members of the Green Party who opposed the sale said it was "mystifying" and "surprising" that the two councils could let the airport go out of public control for such a low figure.

They fear increases in noise and pollution when the airport is a commercially-run venture with plans to develop new routes.

Moyra Martin, who has campaigned against the sale of the airport and stood for election in the Adur area for the Green Party, said: "It is very surprising it has been sold for so little. Very strange.

"The whole process of the sale has been a complete mystery to a lot of us because the people who live around the airport have not been consulted."

Eric Williams, secretary for the campaign group Communities Against Runway Expansion (CARE) said: "It is very surprising how they have reached that value if the auditor said it was worth £21 million.

"We have been completely opposed to the airport sale anyway, right throughout the whole process. There are three schools which will be affected by noise pollution and covered in nitrous oxide if there are more flights."

Worthing councillor Bob Smytherman admitted his council was "just glad to be shot" of the airport and said it had become a burden on the taxpayer.

He said: "It was becoming a liability and I think most of us said it has nothing to do with Worthing. It is not in our patch.

"The view was we were just glad to hand it over to someone else."

Brighton and Hove city councillor Keith Taylor said: "I can only go on what the professionals have told us it is valued at but we have been told wildly different figures.

"I was entirely opposed to the airport being sold because we all know it is now going to be expanded and the reason it is going to be expanded is for profit."

Simon Burgess, leader of Brighton and Hove City Council, said: "The proceeds from the sale will enable the city council to significantly step up our investment in improving customer services."

Neil Bellis, chief executive of the Erinaceous Group, said: "We are very proud to be the new owners of such an exciting aviation centre. We believe there is enormous potential to attract new employment opportunities to the airport."

The company has confirmed plans for flights to Edinburgh, Paris, Amsterdam and Dublin.

It has plans for a dedicated railway station, a visitor centre, aviation academy, a business park, leisure services and mixed commercial activities.