Union bosses have slated the management of Manston airport for failing to enter "meaningful" talks to save the airport as rumours emerge of a new offer to buy it.

Unite says it understands US group RiverOak Investment Corp is making an "improved" bid for the site today.

The Connecticut-based consortium had a £5million offer rejected for the airport last week - shortly before owner Ann Gloag announced the site's closure, saying no "viable alternative" had been found.

Unite will help its members launch formal grievances against parent company Manston Skyport Ltd for failing to give a "coherent reason" for the closure.

The 144-strong workforce – of which about half is represented by Unite – had its final consultation meeting with management today ahead of its closure on Thursday.

It comes as protest group Save Manston carries out a PR stunt today, driving two cars from the House of Commons to Gatwick and Manston respectively and timing the two journeys.

Unite regional officer Ian McCoulough said: "We will be taking legal advice to support our members in taking out grievances against the company for its abject failure to enter into meaningful talks with Unite to save the airport and the jobs of the workforce.

"The closure of the airport could also adversely affect up to 500 more jobs in the wider supply chain.

"We understand that RiverOak may be making an improved offer today. If this is not accepted, the airport will close on Thursday which will be a heavy blow for the staff and a sad day for Kent."

He added: "We believe Manston should continue as a viable airport. It is vital to the local economy in terms of employment and economic growth in the county."

Manston was bought by Stagecoach founder Ann Gloag for £1 in November.

The airport dates back to the First World War and was heavily bombed during the Battle of Britain in the Second World War.