Economic Development chief executive Mike King said that his department had always intended to invoke a clause in the contract with Canbedone Productions unless the project moves forward by that deadline, which is now just five months away.
The commitment comes two years after Economic Development granted the company £200,000 to help make the fantasy film Knights of Impossingworth, parts of which would be shot in Jersey and which could star famous names like Bill Nighy.
Mr King, who was speaking after a report by the States spending watchdog criticised his department for what it called a catalogue of mistakes in its handling of the grant, said he was still confident that the film would be made.
