LONDON, Oct. 28 (UPI) -- EU Budget Commissioner Jacek Dominik warned U.K. Prime Minister David Cameron Monday that he risks opening "Pandora's box" by refusing to pay its 1.7 billion pound ($2.6 billion) bill.
Cameron said the EU "had another thing coming" if it expected the U.K. to pay the 1.7 billion pound bill before Dec. 1.
He told Parliament Monday that the U.K. will defend its national interests and the EU must work to regain the trust of its members.
Dominik said this resistance is opening "Pandora's box" for future relations with the EU including negotiations over resource decisions and the U.K. rebate. He also warned that fines can be imposed on the amount the U.K. owes.
A spokesman from Downing Street said the rebate will not be put on the negotiating table.
"By law, member states are obliged to pay their contribution. I was surprised by the reaction [from David Cameron] because up to this moment there was no single signal from the U.K. administration that they have [a] problem with this figure. Never in the past there was a situation that such a decision was changed because one of the member states have contested," said Dominik. "So if you open this act for future negotiations you open a Pandora's box."
President of the European Commission, Jean-Claude Juncker, said Cameron would be a "coward" if he didn't pony up.