A deal to introduce a new fleet of search and rescue helicopters has been put on hold by the government after information relating to the bid process fell into the hands of the preferred bidder.

The privatisation of Britain’s air-sea rescue service, currently run by the Royal Air Force, was thrown into doubt last month after Royal Bank of Scotland pulled out of the Soteria consortium which was last year named preferred bidder for the 6 billion pound contract.

The service has 12 bases across the UK including one at Wattisham in Suffolk.

Other members of the consortium had included Sikorsky, part of United Technologies Corp, French defence group Thales and Canadian helicopter services firm CHC Helicopter.

Philip Hammond, the secretary of state for transport, said in a statement that Soteria had informed the government in December of irregularities concerning the conduct of their bid team.

Irregularities included access by CHC Helicopter to commercially sensitive information regarding official evaluations of bids, he said, and evidence that a former member of the government’s project team had assisted the consortium in preparing its bid.

“The government has sufficient information to enable it to conclude that the irregularities that have been identified were such that that it would not be appropriate to proceed with either the preferred bid or with the current procurement process,” Hammond said in a statement.

Ministry of Defence police are still investigating the incident, he said, adding that the government was looking at potential procurement options for continuing the service which currently uses an ageing fleet of Westland Sea King helicopters.

The consortium had been due to take over search and rescue for 25 years from 2012.