The former Prime Minister made his remarks as the Government confirmed the precise time and date of Brexit will be written into law, with the UK set to leave the EU at 11pm GMT – midnight in Brussels – on 29 March 2019.
Mr Brown insisted he is not arguing for a second referendum “at this stage” but predicted there will come a point when Leave voters conclude that Brexit will not deliver what was promised.
Mr Brown, a Remain campaigner, said in an interview with the BBC that many Brexiteers could still be persuaded of the case for Remain if they were presented with “new evidence”.
“Is there something that we didn't get right the last time that could persuade millions of Leave voters that it was worth going Remain?” Mr Brown – who kept the UK out of the Euro saying the time was not right for the single currency – said.
Almost 52 per cent of those who voted in the 2016 Referendum backed Brexit, but Mr Brown said he believes it will become clear to many by next summer that the decision to leave will not deliver the UK what the Leave campaign promised – including an extra £350m a week for the NHS.
“I would not try to tell people that they were wrong,” he said, acknowledging that people had voted Leave for “very real reasons” that should be “respected” in a democracy.
But, he said, there “may be scope" for a reassessment.
“I can’t tell you exactly what’s going to happen.. but by next summer the public will have made up their minds that the four red lines that the Government had actually set in place are not going to be achieved.
“So we will not have proper control of our borders, we will not have control of our money, we will be paying loads of money to the European Union, we will not have proper control of our courts because we will still be governed in many ways by the European Court of Justice, we will not have proper control of trade because we will not have individual trade agreements for years.”
But as David Davis prepares for the latest round of negotiations in Brussels, the Brexit Secretary said the amendments currently going through Parliament will make the UK’s departure from the 28-state bloc “crystal clear”.
And Theresa May issued a blunt message to pro-Remain MPs not to attempt to derail the Brexit process.
Writing in the Daily Telegraph the Prime Minister said: ”We will not tolerate attempts from any quarter to use the process of amendments to this Bill as a mechanism to try to block the democratic wishes of the British people by attempting to slow down or stop our departure from the European Union.“
Mr Davis indicated that he was talking a ”pragmatic“ approach to MPs' concerns by writing Brexit day into the Bill.
He said: ”Our amendment makes it crystal clear that the UK is leaving the EU at 11pm on March 29 2019.
“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.
”This important step demonstrates our pragmatic approach to this vital piece of legislation.
“Where MPs can improve the Bill, whatever their party, we will work with them.
"We look forward to further debate in the House of Commons when committee stage begins next week."
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