French President Francois Hollande has warned Britain that its exit from the European Union would have its own costs, saying London should pay the price for the decision.

"There will inevitably be a price and a cost for Britain, it's the choice they made," Hollande said on Saturday as he arrived for an EU summit to adopt guidelines for negotiations on Brexit, or Britain’s pullout from the bloc.

Hollande said the EU would not let Britain have a soft Brexit, saying the continental bloc would do its best to engineer a process that would ensure benefits for Brussels rather than for London.

"We must not be punitive, but at the same time it's clear that Europe knows how to defend its interests,” said Hollande, adding, “Britain will have a less good position outside the EU than in the EU.”

The French leader rejected suggestions that a snap election in Britain would allow Prime Minister Theresa May to strengthen her position in the talks with the EU.

“The EU's principles and the objectives are already fixed, these will be the lines chosen by negotiators,” he said, adding, “I can understand the electoral argument but it will not influence the EU.”

Other EU officials have also dismissed the idea that early elections in Britain could give the ruling conservative party an advantage in future talks with the EU.

Luxembourg Prime Minister Xavier Bettel (shown above) said the EU was fully united on how to deal with the issue of Brexit.

“We are very united, you seem surprised, but it's a fact,” Bettel said, adding, “It's an internal problem she wants to resolve in the Conservative party, to have not a hard Brexit or a soft Brexit, but Theresa's Brexit.”

EU leaders agree Brexit negotiating guidelines

European Union leaders unanimously adopted their Brexit strategy on Saturday, agreeing on the guidelines for the bloc’s negotiations with London during their first meeting without the UK since the British premier triggered the exit process a month ago.

"Guidelines adopted unanimously. EU27 firm and fair political mandate for the Brexit talks is ready," EU President Donald Tusk, who chaired the meeting, said on Twitter, shortly after the summit started.

An EU source said the 27 leaders had adopted the eight pages of the negotiating guidelines hammered out by their diplomats, unchanged, within one minute.

The negotiations are to start shortly after early general elections in Britain on June 8.