She will pledge to secure the unprecedented deal covering goods and services in her latest major Brexit speech on Friday – but has already been accused by domestic critics of proffering “empty slogans”.
Even as she put finishing touches to her text, top EU politicians also claimed she can only seek a less ambitious trade deal “based on the foundation of realism”, given her refusal to compromise on key issues.
It was also reported on Thursday that there is still disagreement in her Cabinet on whether her speech should offer a “binding commitment” to align with some EU rules in the future.
The speech follows days in which Ms May has clashed with EU leaders over the UK’s insistence that it can keep an all but open border between Northern Ireland and the Republic, while also leaving the EU’s customs union.
It had originally been scheduled to take place in the North East but the venue was changed at the last minute with storms and snowy weather hampering travel.
Instead, the Prime Minister will go to Mansion House in London, where she will say: “What I am seeking is a relationship that goes beyond the transactional to one where we support each other’s interests.
“So I want the broadest and deepest possible agreement – covering more sectors and co-operating more fully than any free trade agreement anywhere in the world today.”
Her “five tests” approach echoes Gordon Brown’s for joining the Euro – but unlike the ex-Labour PM’s proposals, Ms May’s tests set out equivocal principles that should be met instead of specific economic ones.
The first is that the deal must respect the referendum result, and allow the UK to “take control of our borders, laws and money” – a likely reference to her plan to remain outside of any customs union, the European Court’s reach and stop payments to EU coffers.
The second is that “the new agreement we reach with the EU must endure…[and that the UK and EU] must not find ourselves back at the negotiating table because things have broken down”, which one insider said aimed to urge the EU to be reasonable in its demands.
The others are “protecting our security and prosperity”, “delivering an outcome that is consistent with the kind of country we want to be”, and “bringing our country together”.
The Prime Minister will also say her vision is one of a UK that is a “champion of free trade based on high standards”, in a bid to allay fears that Britain will become a Singapore-style economy off the coast of mainland Europe.
Critics immediately rounded on the Prime Minister, with Labour MP Chuka Umunna MP, leading supporter of the Open Britain campaign, saying: “They are still pretending we can have our cake and eat it – this is fantasy land.”
Former Labour transport secretary Lord Adonis said: “After 20 months of chaos, this speech shows the Prime Minister still doesn’t have a credible Brexit policy.
“It’s just more empty slogans appealing to both sides in the Tory civil war, followed by surrender.”
Ms May and her Cabinet spent two hours reading and discussing the text at a meeting at Number 10 on Thursday morning.
While the official line is that they unanimously agreed the speech is a “real step forward”, officials accepted that the speech would only be “finalised” after the meeting, indicating changes were possible.
One point of contention said to have arisen relates to whether the UK should make a ‘binding commitment’ to align with EU rules and regulations in certain sectors – something Foreign Secretary Boris Johnson and Brexit Secretary David Davis pushed back on.
One Brexiteer Cabinet Minister told The Independent he had made suggestions for changing the speech which he believed the Prime Minister had taken on board, adding: “I’m happy with it.”
Ahead of a meeting with Ms May at Number 10, EU Council President Donald Tusk warned that any trade deal would not deliver the same benefits as the single market.
“There can be no frictionless trade outside of the customs union and the single market”, he said, echoing the phrase used by Ms May.
“Friction is an inevitable side-effect of Brexit by nature.”
With the intervention just hours away, chief EU Negotiator Michel Barnier said the UK had to seek a deal “based on the foundation of realism” and could not avoid making hard choices.
He told business groups he hoped Ms May’s address would “help us move the negotiation forward”, but he warned: “Any vision of the future must take into account the fact that the EU cannot and will not compromise on its founding principles.”
Ms May’s approach to Brexit has seen her insist the UK can leave the EU and its customs union while also keeping the border in Ireland all but open, something which is seen by many as critical to peace in the region.
But earlier this week Mr Barnier published a draft withdrawal agreement text, which proposes a “common regulatory area” across Ireland if other solutions to avoid a hard border fail.
It would create a customs border in the Irish Sea unless Ms May agrees to full alignment across the UK – effectively keeping the entire UK in the EU customs union and single market, which she has ruled out.
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