French President Emmanuel Macron has said Brexit cannot proceed until three major sticking points have been clarified, following Theresa May's speech in Florence.

Mr Macron said the settlement rights of EU nationals living in the UK, the financial terms of the exit package and the Irish question all require further clarification before the negotiations can continue.

He said he noted "progress" and "openings" in the key speech delivered by Ms May, but was still left needing answers to the three key questions.

"The signals sent by the British Prime Minister show a will", he told the French press.

"Before we move forward, we want to clarify matters concerning the settlement of European citizens, the financial terms of exit and the question of Ireland.

"If these three points are not clarified, we will not be able to advance on the rest."

Theresa May hoped her speech in Florence would provide clarity on the UK's Brexit negotiating position (EPA)

He added that he would leave "the exclusivity" of the reactions to the chief EU negotiator Michel Barnier.

"On two of these points (...) openings have been made, it is up to Michel Barnier to comment on them."

Mr Barnier earlier welcomed "the constructive spirit" of the speech in Italy - but asked for further details on its "concrete implications", particularly in regards to Ireland.

The Brussels chief said the Prime Minister had failed to clarify how the UK would honour its "special responsibility" for the consequences of Brexit for Ireland.

Ireland's Taoiseach Leo Varadkar joined the call for greater detail on how a transition period might work after the UK leaves the Union in 2019, while Sinn Fein president Gerry Adams said Mrs May delivered nothing but the same old story.

Mr Barnier said: "Today's speech does not clarify how the UK intends to honour its special responsibility for the consequences of its withdrawal for Ireland.

"Our objective is to preserve the Good Friday Agreement in all its dimensions, as well as the integrity of the Single Market and the Customs Union."

But the leader of the Government's DUP allies Arlene Foster offered support, claiming Ms May had outlined a positive vision for the future in the speech.

Following Brexit, the UK's only land border with an EU state will be that between Northern Ireland and the Republic and working out how this will operate in practice when freedom of movement ends is one of the chief points of negotiation.

"The UK government, the Irish government and the EU as a whole have been clear that through the process of our withdrawal we will protect progress made in Northern Ireland over recent years - and the lives and livelihoods that depend on this progress.

"As part of this, we and the EU have committed to protecting the Belfast Agreement and the Common Travel Area and, looking ahead, we have both stated explicitly that we will not accept any physical infrastructure at the border.

"We owe it to the people of Northern Ireland - and indeed to everyone on the island of Ireland - to see through these commitments."

She proposed a two-year transition period for the UK after its leaves the EU, suggesting that Britain would continue to "honour its commitments" under the bloc's current budget.

Much of the speech delivered exactly what was expected, with Ms May proposing a transition period of "about two years" following the UK's exit from the 28 nation block in March 2019, during which time trading relations will remain as they are in order to avoid the much-feared economic "cliff edge".

In her 35-minute address, Ms May insisted there should be no need for new trade tariffs between the UK and EU and promised any future UK divergence from EU rules would not be designed to gain an "unfair competitive advantage".

The speech was hailed as "positive, optimistic and dynamic" by Foreign Secretary Boris Johnson, who was in the audience just six days after publishing his 4,000 word personal Brexit manifesto which exposed Cabinet rifts over the future relationship and was widely viewed as his personal manifesto.

But Mr Johnson admitted it could take until 2021 to fully repatriate powers back to the UK as promised by the Leave campaign, telling reporters: "As the Prime Minister rightly said we are going to have a transition period and after that of course we are going to be taking back control of our borders, of our laws, of our destiny."