The British legal expert who wrote Article 50 will make a major speech on Friday accusing Theresa May of “misleading” the public over whether Brexit can be reversed.

Former diplomat Lord Kerr will condemn the Prime Minister for making a “political decision” to withhold the truth, that the Government can unilaterally stop Brexit any time it likes.

His latest intervention is the first time he has directly attacked Ms May for failing to be straight with voters about it, with her and her ministers refusing to give clear answers on whether Article 50 can be revoked.

He will also demand Downing Street stop suppressing the release of legal papers proving his case, arguing that the public has a right to know how the country can easily step back from EU withdrawal.

It comes as the next round of Brexit talks gets underway in Brussels with negotiators still struggling to make progress on the early issues of Britain’s divorce bill, EU citizens’ rights and the Irish border.

Next week more light will also be shed on the compromises the Government has to make in Westminster to push through its Brexit legislation, made all the more difficult since Ms May lost the Conservative majority in the Commons.

Donald Tusk says Brexit can still be stopped

For months when asked if Article 50 is reversible, ministers have refused to go further than saying it is not the Government’s “intention” to do so.

But in a speech at an Open Britain event in London, Lord Kerr will say: “The fact is that a political decision has been made, in this country, to maintain that there can be no going back.

“Actually, the country still has a free choice about whether to proceed.

“As new facts emerge, people are entitled to take a different view. And there’s nothing in Article 50 to stop them.

“I think the British people have the right to know this – they should not be misled.”

For several weeks pressure has been building on the Government to publish legal advice it has received, that is believed to state that Parliament can stop Brexit.

The country’s top legal experts are said to have told the Prime Minister that leaving the European Union could be halted if MPs judge that a change of mind is in the national interest.

Lord Kerr, who was Britain’s permanent representative at the EU before becoming ambassador to the US, will say: “The Government give the impression that the Rubicon has been crossed, but they currently refuse to publish their law officers’ opinion: I think we know why.

“They have been careful not to say that we could not take back Mrs May’s letter.

“During the Miller case, and at the Despatch Box in both Houses, Government spokesmen have consistently said only that “as a matter of firm policy”, we won’t take it back.

“That formula in itself confirms that we could take it back.”

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

Polling for The Independent has shown that there is a shift in attitudes towards Brexit with the change potentially accelerating amid a grim economic outlook for the UK.

The exclusive survey in October showed that once “don’t knows” were redistributed, the country backed remaining in the EU by 52 per to 48 per cent.

Conservative MPs have warned Ms May that her own leadership hinges in part on being able to make progress in stalled Brexit talks, with Brussels currently demanding the UK commit to paying a larger divorce bill before any lucrative future trade partnership can be discussed.

But the longer Brussels refuses to allow talks to move on, the closer the prospect of a no-deal Brexit comes, something that industry figures and economic experts have suggested would be a catastrophe for the British economy.

The Government also faces a legislative quagmire in Parliament, trying to push through what is one of the most complex legislative programmes in 18 months without having a majority in the House of Commons or the House of Lords.

A string of European politicians including French President Emmanuel Macron, Irish Taoiseach Leo Varadkar and President of the European Council Donald Tusk have indicated that the “door remains open” if Britain wishes to change its mind.

Lord Kerr’s call comes as David Davis, the Brexit Secretary, announced that Britain’s “exit day” from the European union will be put on the face of the EU Withdrawal Bill – a concession to the Eurosceptics on the Conservative backbenches.

The Department for Exiting the European Union added it would “put this issue to rest” and table an amendment to “remove all doubt” over Britain’s departure date.

“Our amendment makes it crystal clear that the UK is leaving the EU at 11pm on 29 March 2019,” Mr Davis said. “We’ve listened to members of the public and Parliament and have made this change to remove any confusion or concern about what ‘exit day’ means.