In a keynote speech to parliament attended by Prime Minister Theresa May, the Dutch royal said seeing Britain go its separate way "truly saddens us".

London and Brussels should pay "special attention" in their negotiations about the fate 100,000 Dutch citizens in Britain and 50,000 Britons living in the Netherlands, he said.

"Many of them have lived and worked here for many years," Willem-Alexander said.

"Yet all these individuals now live under the shadow of uncertainty about their future status," said the royal.

"I understand how difficult this is for them and I trust this uncertainty will be resolved."

The Brexit referendum prevailed in 2016 thanks in part to support from Britons who wanted the UK to regain control over its border.

May has said that EU citizens will no longer be givin priority rights to live and work in Britain after Brexit.

But the terms of Britain's exit are still under discussion, and the issue of EU and UK expats' rights is still not finalised.