The EU’s Brexit negotiator Michel Barnier said on Tuesday that talks on a future trading relationship with Britain will be difficult, as the bloc “will not tolerate unfair competitive advantage,” Reuters reports.

Speaking during Europe’s largest tech event, the Web Summit, in Lisbon, he said that “the UK should not think that zero tariff, zero quotas will be enough.” The official added that time would also be “extremely short” to negotiate a new partnership.

“I know this negotiation will be difficult and demanding,” he said, listing state aid, social and environmental rights, and taxes as top priorities for the European Commission.

“Even when the [Brexit] deal is ratified it will not be the end of the story… We have to build a new partnership with the UK after they withdraw.”