Cornwall and the Isles of Scilly have pressed the government for assurances about future investment in the wake of Brexit.
The Local Enterprise Partnership have jointly written to the Secretaries of State whose departments currently control EU funding.
The letters, signed by Cornwall Council Leader John Pollard and LEP Chair Mark Duddridge, highlight concerns about the future of a raft of proposed investments aimed at creating jobs and growth.
Cornwall and Scilly were earmarked for around £500 million of EU investment from 2014 to 2020 to close the economic gap with other parts of Europe by growing businesses, creating jobs and boosting skills.
The Brexit vote has put a question mark over that funding, despite assurances from the Leave campaign it would be honoured in full to 2020.
The Treasury announced on August 13 that EU-funded projects signed by the time of the Autumn Statement later this year would have their funding guaranteed.
There was a similar pledge on research funding and farm payments up until 2020, all of which was broadly welcomed.
But with no further guarantees this still leaves at risk around £300m of EU funding earmarked for Cornwall and the Isles of Scilly.