Britain is open to some flexibility on the mechanism that would allow Northern Ireland politicians to decide whether it remains in regulatory alignment with the European Union as set out in Britain's latest Brexit deal proposals, Brexit Secretary Stephen Barclay has said.

"The key issue is the principle of consent, that's why the backstop was rejected three times, that was the concern in terms of both sides in Northern Ireland not approving of the backstop," Mr Barclay told the BBC's Andrew Marr on Sunday.

"So the key is the principle of consent, now of course in the mechanism, as part of the intensive negotiations we could look at that and discuss that."

Mr Barclay defended the Brexit plan, saying the UK government has put forward "very serious proposals" to leave the EU in a "smooth way".

He said they need to get into intense negotiations now with the EU and what the UK is clear on and committed to is securing a deal.

Mr Barclay said the proposals put forward on a regulatory zone has the "crucial addition of consent" in order to address previous concerns.

He said the UK would be willing to discuss how it is implemented with the EU in the coming days.

Regarding customs, he said it is worth looking at what objections the EU has.

"The impact on the all-Ireland economy seems to be the key issue," Mr Barclay said.

He said that trade from Northern Ireland into Britain is four times more than into Ireland.

Mr Barclay said if Britain does not get a deal in time, the Benn Act will be applied and he confirmed the government will abide by the law.

Taoiseach Leo Varadkar, however, has said that while a deal on Brexit is still possible, the current proposals put forward by the UK do not form the basis for deeper negotiations.

Speaking at a Fine Gael event in Dublin last night Mr Varadkar said  problems remain around the issues of consent and the prospect of customs checks.

He said there was a general view across the EU that an extension was better than a crash out, but said it would have to be granted for a good reason.

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The Taoiseach also said that he believes a deal is still possible around a number of key issues.

British Prime Minister Boris Johnson has urged the European Union to show that it is willing to compromise with the UK on a Brexit deal. 

Writing in a number of UK newspapers today, Mr Johnson appealed to the EU to begin serious negotiations, saying that his proposals are picking up support among MPs on all sides.

Meanwhile, also speaking on the Andrew Marr Show, the Prime Minister of Latvia, Krišjanis Karinš, has said in order for a Brexit deal to happen, the UK offer must not be "a take it or leave it".

He said he believes a deal can still be done if the current UK proposal is open to more negotiation. 

He said it is all dependent on "the will" of UK Prime Minister Boris Johnson and if he is willing to negotiate it is a very good sign.

"I have full trust in the (EU) commission to find a compromise."

He said the bulk of the withdrawal agreement has been agreed by both sides and it now depends on one crucial element.

"What is important is the single market remains, Ireland is within it in any arrangement and it doesn't threaten it and how Northern Ireland trades."

He said the EU does "not have a whole lot of wriggle room" and in a short time frame that poses more difficultly.

A member of the European Parliament's Brexit Steering Group has said there is absolutely no chance of getting a deal from Mr Johnson's Brexit plan.

Speaking on RTÉ's This Week, Belgian MEP Philippe Lamberts said it is basically a "rehash of old ideas" both on the regulatory and customs aspects.

He said the more they read the proposal the more they believe it is "a "sham",  in the sense that the UK asks the EU for an open border between Northern Ireland and the Republic but "without any guarantee that the required regulatory alignment would ever come to reality".  

Additional reporting PA