Britain must “come to terms with the fact it’s now a small country”, the Irish Prime Minister has said, in comments that prompted outrage just days before Brexit.

Leo Varadkar also suggested the UK could rejoin the EU if Brexit does not “work out for them” and said Brussels would have the “stronger hand” in trade negotiations.

The Taoiseach’s comments, which come before trade talks begin in March, appeared to be deliberately provocative in a week which will end with Britain celebrating its new-found freedom from the EU.

One former Brexit minister suggested he would serve the Irish people by trying to “work in harmony” with Ireland’s biggest trading partner “rather than trying to provoke it”.

It came as Downing Street announced that ministers would be bypassed in the Brexit trade negotiations, with a team of civil servants called Taskforce Europe, headed by Mr Johnson’s chief Brexit adviser David Frost, carrying out the talks.

It means there will be no role for the International Trade Secretary Liz Truss, raising question marks about her future ahead of an impending Cabinet reshuffle.

Mr Varadkar met the EU’s chief Brexit negotiator Michel Barnier in Dublin on Monday, after which Mr Barnier warned that “time is very short” to conclude a trade deal by the end of the year.

The Irish premier told the BBC: "The European Union is a union of 27 member states. The UK is only one country. And we have a population and a market of 450 million people.

"The UK, it's about 60 (million). So if these were two teams up against each other playing football, who do you think has the stronger team?”

He added: “I don’t think the UK has yet come to terms with the fact it’s now a small country.”

Ireland has a population of 5 million and a gross domestic product of £315 billion, making it the world’s 46th-largest economy. The UK, with a population of 67 million, has a GDP of £2.3 trillion, and is a member of the G7 group of the world’s most advanced economies, as well as being one of the five permanent members of the UN Security Council.

Mr Varadkar said: “On Friday, the United Kingdom is leaving the European Union, we'll say goodbye to an old friend embarking on an adventure.

"We hope it works out for them. But if it does not, there will always be a seat kept for them at the table."

David Jones, the former Brexit minister, said: “He is saying that for a domestic audience, because he has an election coming up, but the fact is that Ireland shares far more with Britain than it does with continental Europe.

“Rather than trying to provoke its most important trading partner, it would do well to work in harmony with it.”

Speaking in London, Mr Johnson again insisted it should be possible to "wrap all this up" by the end of the year.

He said: “We will be doing things very fast, (in a) very friendly and respectful way, and in a way also, I think it's important to stress, that really ensures we look after the interests of the Republic of Ireland as well.”

Downing Street confirmed on Monday that Steve Barclay, the Brexit Secretary, will be out of a Government job on Friday night, as his department will be abolished as soon as Britain leaves the EU at 11pm.

He will have to wait for a reshuffle expected within days of Brexit to find out if Mr Johnson has another ministerial role for him.

Liz Truss, the International Trade Secretary, will play no part in the Brexit negotiations after Number 10 said Mr Frost would be in charge of the Taskforce Europe team of negotiators, reporting directly to the Prime Minister.

A source close to Ms Truss said: “This was always the plan, that DIT would concentrate on the rest of the world while David Frost dealt with the EU.”

Mr Barnier said in a speech in Belfast that he hoped Britain was "reflecting carefully" on how much it wanted to diverge from EU standards, because it was central to defining the future trading relationship.

Separately, Brussels reaffirmed its intention for the European Court of Justice (ECJ) to enforce regulations on fishing, trade and security after Brexit. Downing Street insisted that the ECJ could not be a neutral arbiter, but an internal Brussels memo called for the court to be involved to try to "secure consistent interpretation" of a deal.

The Times reported diplomats have been briefed the UK will be a "partner like no other" after the transition period ends and Britain leaves the EU's jurisdiction.