Manston airport incurred losses of more than £100 million in its 16 years of private ownership and was losing £100,000 a week before it was closed by former owner Ann Gloag.

The figures have been published in a Kent County Council report, which says it is time to “look for a B Plan” for the site after it failed as a commercial operation.

The report, which will be seen as a defensive move after the council was criticised by MPs this month, said councillors believed Mrs Gloag wanted to keep the airport open and discredited US group RiverOak, who unsuccessfully tried to buy the site from her.

It said the new owners of Manston, Chris Musgrave and Trevor Cartner, who own 80% of the site, have “a strong track record in taking over large difficult sites following the demise of earlier uses”.

The pair bought the former home of Pfizer in Sandwich in 2012, turning it into a home for more than 100 companies known as Discovery Park.

The report said the airport never made a profit since the Ministry of Defence sold RAF Manston in 1998, with three companies – the Wiggins Group, Infratil and Lothian Self owned by Ann Gloag – all failing to make it viable before it closed last May, costing about 150 jobs.

It said Wiggins Group, after renaming to Planestation, had hoped to handle 750,000 passengers a year on its EUJet service but only carried 62,709 in its busiest month in early 2005 before it became insolvent and went into administration.

The airport incurred losses of more than £3 million a year when it was owned by Infratil Limited, the New Zealand firm which sold the venture to Mrs Gloag for £1 in 2013.

Appearing to sympathise with Mrs Gloag, the report said: “From the discussions that Kent County Council had with her and her team we believed that she had every intention to maintain and grow the aviation business at Manston airport.”

The council says it tried to meet several times with RiverOak, the US firm which tried to buy the airport before it closed, but that the group declined saying their business plan was confidential.

The report also said the council met PwC, the agents selling the airport, with a view to helping find a viable new owner or operator.

Over 18 months discussions were held with 30 interested parties, including low cost airline operators and private investors, many of which were introduced to PwC by Kent County Council.

It said: “In the event, two of the shareholders of Discovery Park Limited made an approach to Mrs Ann Gloag which subsequently led to their purchase of the airport.

Paul Carter, leader of Kent County Council, said: “I would like to make it abundantly clear that in my 10 years as Leader of Kent County Council I have done everything in my power to help and support the economy of East Kent. I believe that this document demonstrates and evidences exactly that.”

The report – entitled Manston Airport under private ownership: The story to date and the future prospects – will be seen as another defensive move by the council after it was criticised by MPs on the transport select committee for failing in its duty as a local transport authority by allowing the airport to close.

Mr Carter has since described the findings as a “travesty”.