Energy giant Statoil has halted work on a North Sea development following Chancellor George Osborne's decision to increase tax on the industry.
The Norwegian firm said it will "pause and reflect" on the future of its Mariner and Bressay fields near Shetland.
The comments were made as oil and gas industry leaders called an emergency meeting following the tax increase.
Mr Osborne has defended his decision to impose the £2bn charge, designed to fund a 1p-per-litre drop in fuel duty.
Statoil said it was due to start production at Mariner in 2016/17, with work expected at Bressay later. Estimated reserves for the two fields were put at 640m barrels of oil. The firm intended to operate the fields from Aberdeen.
Statoil spokesman Bard Glad Pedersen said: "The proposed tax change has significant impact on the project economics of Mariner.
"We have to pause and reflect to evaluate what impact this will have and consider how to proceed after this."
Industry body Oil -amp; Gas UK has warned the decision could jeopardise thousands of jobs.