Up to 45,000 new homes would be needed if a new runway is built at Gatwick.

That is the conclusion of a study by independent consultants commissioned by West Sussex County Council and the business-led Gatwick Diamond Initiative.

The report claims the housing – which is the equivalent of a town larger than Hove – would be needed to cope with a vastly increased workforce, dozens of new firms and the infrastructure required for the expanded airport.

Brendon Sewill, chairman of the Gatwick Area Conservation Campaign (GACC), said: “This independent study, if correct, shows that a new runway would lead to widespread urbanisation, serious pressure on schools and hospitals, and the loss of much dearly-loved countryside.

“The more we find out, the more we doubt if the implications of the study were taken on board by members of the county council before they took their surprise decision in July to support a new runway.”

He added: “The Gatwick Diamond businessmen, who have been lobbying to promote a new runway, also have some explaining to do. They sponsored this study so they can’t disown it.”

The prediction was included in a document published by the local authority titled “Implications of changes to airport capacity”.

Up to 5,000 new homes would be needed in 2015-2020, 15,000 in 2020-2025 and 25,000 in 2025-2030.

Jeremy Taylor, chief executive of Gatwick Diamond Business, said he supported the findings but described their presentation as “alarmist”.

He said: “What the report also found was that if we don’t support a second runway we will see a decline of 10,000 jobs.

“GACC need to explain how our economy will recover should the runway be built elsewhere.

“The figures are alarmist. Maybe we could see 30,000 houses over ten to 15 years after 2025.”

It comes as Crawley and Horsham councils are struggling to find suitable sites for a few thousand houses.

Both are currently in the process of adopting their development plans, which will map out their area’s blueprint for the next two decades.

Gatwick Airport has been making its case for a second runway to submit to the Aviation Commission.

Recommendations will be made to Government on potential runways after the next general election in 2015.