Prime Minister Theresa May admitted that the UK will lose influence on the rules governing the European economy, as she invoked Article 50 of the Lisbon Treaty and started the two-year-long Brexit talks on Wednesday (29 March).
"We understand that there will be consequences for the UK of leaving the EU. We know that we will lose influence over the rules that affect the European economy," the Conservative premier told the House of Commons.
"We know that UK companies that trade with the EU will have to align with rules agreed by institutions of which we are no longer a part, just as we do in other overseas markets. We accept that.
"However, we approach these talks constructively, respectfully, and in a spirit of sincere cooperation."
May argued it was in the interests of both the UK and the EU that the parties use the negotiations to "deliver our objectives in a fair and orderly manner".
"And it is in the interests of both the United Kingdom and the European Union that Europe should remain strong, prosperous and capable of projecting its values in the world," she said.
Labour leader Jeremy Corbyn urged May to make sure the UK maintains its full access to the EU's single market, while the British Chambers of Commerce (BCC) demanded answers to "practical questions" from firms across the UK.
"A pragmatic and grown-up dialogue on the real-world issues, rather than verbal volleys between London and Brussels, would give firms greater confidence over the next two years," said Adam Marshall, director general of the BCC.
"In the early weeks of the negotiation process, businesses would like to see an effort to secure simultaneous exit and trade talks. Concluding exit and trade negotiations at the same time would moderate adjustment costs for UK businesses, and enable trade between UK and EU firms to continue with less disruption."
Elsewhere, Liberal Democrat leader Tim Farron claimed May had thrown British business into a state of "uncertainty and powerlessness" by quitting the EU and seeking a bespoke customs union agreement, which would allow the UK to broker its own free trade deals.
"This is May's choice to go for a hard Brexit. It wasn't on the ballot paper, and the Conservatives in their election manifesto said we should stay in the single market," said Farron. "That is why we will continue to fight to give the people a say on the final deal."