A formal offer to buy under-threat Manston airport has been rejected today.

The conditional written bid to keep it as an airport, submitted yesterday, has been turned down this afternoon.

The airport said one of the reasons was that some of those involved in the offer had previously "failed to substantiate proposals".

The airport - bought by Stagecoach Group co-founder Ann Gloag last October for £1 - said it has "clearly demonstrated" a "willingness to consider credible and viable offers".

The announcement throws the future of the airport - and its workers - into further doubt.

A Manston Airport spokesman said: "Following reports made public about an offer to purchase Manston Airport, we confirm a conditional written offer was received yesterday. The basis of this proposal had already been put to the shareholders verbally on Friday and had been rejected.

"The written proposal has been rejected this afternoon. There are a number of reasons for this including the fact that some of those associated with the offer have approached the shareholders previously and have consistently failed to substantiate their proposals.

"We have clearly demonstrated our willingness to consider credible and viable offers and have engaged with a range of interested parties over the last couple of months which unfortunately have not come to fruition."

A consultation into its closure began in March, with estimates the airport has been losing £10,000 a day.

It was bought in October by the co-founder of the Stagecoach Group, Ann Gloag, who paid just £1 for it from New Zealand company Infratil.

After news of the closure emerged, KLM withdrew flights and an earlier offer by an unnamed buyer to acquire the airport was withdrawn.

North Thanet MP Sir Roger Gale had revealed the offer yesterday and said he believed it was viable.

Mr Gale, who has spearheaded efforts to get a sale, said he hoped "any differences between seller and buyer will be resolved".

He also added that Mrs Gloag had indicated she did want to sell.

In March, Mr Gale had urged the government to step in over the impending closure.

Around 150 jobs are likely to be lost if the airport shuts.