A letter written by the Prime Minister will be given to European Council President Donald Tusk on Wednesday to inform him the UK wants to leave the EU, officially starting the legal process of Brexit.
The Tory rebel thundered against Article 50 being invoked tomorrow as he said the battle to keep the UK inside the bloc was not over.
Lord Heseltine told Channel 4: “Oh no. The letter will represent the biggest sacrifice of British sovereignty that I can remember.
“And what’s now going to happen is the Europeans will tell us the conditions on which we can trade with our biggest markets.
Lord Heseltine claimed Brexit is ‘biggest sacrifice of British sovereignty’
“When that becomes apparent all the stuff about gaining sovereignty, putting ourselves in charge, will be exposed for the hypocrisy it was.”
The staunch Remainer claimed Brexit was Margaret Thatcher’s fear realised, as he said the UK would no longer be in control over its own trade and industry.
Lord Heseltine said: “You see what’s happening tomorrow is the one thing that Margaret Thatcher was frightened of, losing control over the conditions in which British Government, trade and industry, actually operates in our biggest market.
“That’s what tomorrow represents; it is the biggest sacrifice of British self-interest I know of.”
He added: “I have no confidence in the decision to rupture our relationship with our allies on the continent of Europe, full stop. Nor did Mrs May in April of last year.”
The letter will represent the biggest sacrifice of British sovereignty that I can remember
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A spokesman for 10 Downing Street has declined to comment on what time Article 50 will be triggered tomorrow, however Mrs May will inform the country by making a statement in the House of Commons.
EU leaders are expected to give a response to the British Government within 48 hours of the notification of the UK’s exit from the bloc.
Last week Mr Tusk said: “When the UK notifies, it is our goal to react with the draft negotiation guidelines for the 27 member states to consider.
“For this I think we need more or less 48 hours. Leaders will then meet, probably in April, to finalise these.”
The other 27 members of the EU will attend a European Council summit on Saturday April 29 to decide their joint negotiating position for Brexit talks.
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Last week, Lord Heseltine took aim at Brexiteers for believing the referendum result would lead to an “enhancement of British sovereignty”.
He said: “I was one of the first to say we should make progress and get on with it because there was a need to end the uncertainty but not for one instance did I believe that we should then conclude by leaving the European Union.
“What I wanted to do and why I suggested that the Brexiteers should be in charge of the negotiations is to let the British people see what sort of deal was available after the negotiations had taken place, which should happen quickly.
“My own view is it will be an inferior deal to anything we’ve got today and the only way to find out whether what I believe is true or what others believe is true is to get on and talk to the European partners.”
He then said the UK would have no choice but to leave the European bloc on the EU’s terms.