PM prepares major Brexit speech after resignation of UK's EU ambassador

Theresa May is preparing to make a major speech on Brexit amid accusations by the disgruntled outgoing top UK civil servant in Brussels that the Government lacks an exit strategy.

Foreign Secretary Boris Johnson and Brexit Secretary David Davis are contributing to the content of the address, which is expected later in January.

The Prime Minister will reportedly say Britain will pull out of the single market if the European Union fails to make concessions on freedom of movement, although No 10 sources insisted the claims were speculation.

Mrs May moved swiftly to draw a line under the row sparked by the surprise resignation of UK permanent representative Sir Ivan Rogers by agreeing his replacement within 36 hours of his notice to quit.

He is being succeeded next week by career diplomat Sir Tim Barrow, a former ambassador to Russia described by No 10 as a "seasoned and tough negotiator" who will help the Government make a success of Brexit.

The appointment was welcomed by Labour but Ukip said the role should have been given to a "committed Brexiteer".

In a fiery resignation letter, Sir Ivan had hit out at the "ill-founded arguments and muddled thinking" of politicians and said civil servants still did not know the Government's plans for Brexit.

It sparked a war of words, with prominent Brexiteers Iain Duncan Smith and Peter Lilley accusing the diplomat of "sour grapes" while former senior civil servant Lord Ricketts attacked the "denigration" of the long-serving mandarin.

Brussels officials said Sir Ivan's resignation meant the UK had lost a "professional" diplomat who had always "loyally defended" his Government.

Foreign Secretary Boris Johnson said Sir Tim was "just the man" to secure the best deal for the UK.

"Tim Barrow has been invaluable since I joined the Foreign Office in July and I want to personally thank him for his relentless energy, wise counsel and steadfast commitment," he said.

"He is just the man to get the best deal for the UK and will lead UKRep with the same skill and leadership he has shown throughout his career. I wish him all the best."

Sir Tim was appointed political director general at the Foreign Office last March after leaving his role in Moscow.

He has had two previous stints working as part of the UK's Permanent Representation to the EU (UKRep).

Mr Davis said: "His knowledge of Brussels means he will be able to hit the ground running at a vital time, and steer UKRep throughout the negotiation period. I am confident that with his help, the UK will be able to forge a new relationship with the EU that works to the mutual benefit of both sides."

Sir Tim said he was "honoured" to be appointed to the crucial role.

A Downing Street spokesman said: "We are delighted that Tim Barrow is taking up this role. A seasoned and tough negotiator, with extensive experience of securing UK objectives in Brussels, he will bring his trademark energy and creativity to this job - working alongside other senior officials and ministers to make a success of Brexit."

Ukip former leader Nigel Farage said: "Good to see that the Government have replaced a knighted career diplomat with ... a knighted career diplomat."

The party's Brexit spokesman Gerard Batten said: "This appointment is a disappointment because the last thing we need is another career diplomat wearing a Brussels jersey.

"The Foreign Office needs a complete and revolutionary shake-up for it must begin to reflect the stated desire of the British people to leave the EU."

Labour called for the Government to set out a clear timetable for the publication of its Brexit plans in the wake of the resignation.

The party's Brexit spokesman Sir Keir Starmer said Sir Ivan's resignation was likely to be a "significant loss" for Britain and raised "a number of serious questions" about the Government's preparations for the talks, which Mrs May has said she will trigger under Article 50 of the EU treaties before the end of March.

He added: "I welcome the appointment of Sir Tim Barrow as the UK's new Permanent Representative to the EU. It is of course vital that there should be no vacuum in such an important role and that the new Permanent Representative should be someone with a strong and distinguished record of service as a diplomat.

"But a number of fundamental questions remain unanswered. In particular, Sir Ivan Rogers' confirmation that the Government lack a plan for Brexit and his statement that the UK does not have a proper and effective negotiating team in place."