The German Chancellor Angela Merkel has warned Britain not to be under any "illusions" in thinking that it will be able to get the same rights as an EU member when it leaves the bloc.

The longest serving leader in the western world added that for Britain to think it could maintain parity would be "wasted time" in negotiations.

"A third-party state will not have the same rights or even superior rights to a member state," Merkel said ahead of a Brussels summit Saturday on Brexit.

"This may sound self-evident, but I have to say this because some in Britain seem to have illusions on this point," Merkel told the German Bundestag.

On Saturday, the 27 remaining members of the EU are to meet in Brussels to draw up their position on negotiations with the UK on its exit from the union.

Speaking on Thursday morning (27 April), Merkel reemphasised her position that talks would only begin on Britain's future relationship to the EU once the conditions of its exit had been agreed upon. This sequence of negotiations "is irreversible", she said.

Describing the position of the remaining 27 states and the EU institutions, Merkel said there was "great agreement on our common negotiating strategy towards the UK".

"We can assume that the remaining 27 members will send out a strong signal of unanimity on Saturday," she said.

Merkel, who has lead Germany for more than 11 years, is currently campaigning to win a fourth term as Chancellor and currently leads in the opinion polls.

Seen by many as the unofficial leader of Europe and the head of the fourth largest economy in the word, Merkel will be vital in deciding the fate of Europe in the months and years to come.