AFP, London

Prime Minister Theresa May yesterday called for a wide-ranging free trade deal with the EU after Brexit, but said it was time to face up to "hard facts" about the economic consequences of leaving the bloc.

In a detailed speech just weeks before starting negotiations on the future partnership with Brussels, May confirmed Britain would leave the European Union's single market and customs union after Brexit in March 2019.

She called for the "broadest and deepest possible agreement, covering more sectors and co-operating more fully than any free trade agreement anywhere in the world today".

But she acknowledged for the first time that Britain may suffer new trade barriers as a result of her move, which is driven by a desire to end mass migration and throw off EU regulations.

"I want to be straight with people

because the reality is we all need to face up to some hard facts... In certain ways our access to each other's markets will be different," she said.

She promised to commit to some regulations and minimum standards on goods in a bid to maintain close

trade ties, while reserving the option for Britain to diverge in the future.

The EU has already dismissed this as "cherry-picking", but May pointed out that each of the bloc's existing trade deals with other countries was slightly different.

"We both need to face the fact that this is a negotiation and neither of us can have exactly what we want," she said in London.

The EU's chief negotiator Michel Barnier welcomed Theresa May's Brexit speech, saying she had brought "clarity".

"I welcome PM @theresa_may speech. Clarity about #UK leaving Single Market and Customs Union & recognition of trade-offs will inform #EUCO guidelines re: future FTA," Barnier tweeted after May's address in London, in which she said said it was time to face up to "hard facts" about the economic consequences of leaving the bloc.

The main opposition Labour party this week came out in favour of a new customs union, which is already backed by the main business lobby groups.

Their change in stance raises the stakes in parliament, which will vote on the final exit deal and where May has only a slim majority.