The European Union has ordered the UK to return £85m (99.4m euros) for failing to comply with rules on agricultural payments.
The charge follows the discovery of "weaknesses" in processing applications for funds and on-the-spot checks.
The demand is part of a call for 22 EU member states to return a total of £357m (414m euros).
The UK's figure - which relates only to payments made to English farmers - is the largest among the 22 states.
Member states are responsible for administering payments under the Common Agricultural Policy.
The EU can demand a refund if "management and control is not good enough to guarantee that EU funds have been spent properly".
The second biggest demand for a return of funds is £41.6m (48.3m euros) from the Italian government.