BORIS Johnson has dismissed a warning from MPs that Brexit may have to be delayed because the UK is unprepared on multiple fronts.

The Foreign Secretary, a leading Leave campaigner, said “great progress” had been in talks with Europe so far, and he was hopeful of a “good deal” later this month.

Theresa May is due to attend a European summit at the end of the week to discuss the final terms of the transition deal which will follow Brexit in March 2019.

Mr Johnson was speaking after a majority of the House of Commons Brexit select committee urged the UK government to consider a “limited extension” to the Article 50 process.

The committee said it was “difficult to see how it will be possible to negotiate a full, bespoke trade and market access agreement” and other deals before October 2018, the deadline the UK government has set for agreeing the “substance” of a future UK-EU relationship.

It said “little progress” had been made on the technical means of avoiding a hard border between North Ireland and the Republic of Ireland.

The committee also said the government should consider extending the transition period after Brexit which the EU wants to run until December 2020.

The conclusions split the committee, with pro-Brexit MPs issuing a “minority report”.

Asked about the prospect of delay on the BBC’s Andrew Marr Show, the Foreign Secretary said: “I don’t think that’s true at all. We’re making great progress in the negotiations and I hope that we’ll get a good deal on the implementation [transition] period in March.

“The House of Commons voted overwhelmingly to trigger Article 50 and let’s get on with it.”

The Sunday Times reported the cabinet was briefed last week that Britain’s customs system will not be ready for the UK’s new relationship with the EU by the end of 2020.

Not enough work has been done on IT, staffing and other key issues, sources told the paper.

Asked if was concerned the transition timetable might slip, Mr Johnson said: “No. What most people in this country want, whether they voted leave or to remain, they want us just to get on and do it.”

On ITV’s Peston on Sunday, Shadow Chancellor John McDonnell agreed the 29 March 2019 date set for Brexit might have to change, but by days or weeks rather than months.

He said: “We said there shouldn’t be a hard deadline, there should be some flexibility [but], not a long period of time.

“It’s ludicrous setting a hard and fast date like that but we also said have a proper transition period, we said, well, as long as necessary, short as possible, we said about two years.

“We said flexibility, but we’ve got to respect the outcome of the referendum as well."

Labour MP Hilary Benn, chair of Commons Brexit committee, said the negotiations were at a “critical stage”, with just seven months to decide “a whole host of highly complex issues”.

He said: “The Government must now come forward with credible, detailed proposals as to how it can operate a 'frictionless border' between Northern Ireland and the Republic of Ireland because at the moment, the Committee is not persuaded that this can be done at the same time as the UK is leaving the single market and the customs union.

“We know of no international border, other than the internal borders of the EU, that operates without checks and physical infrastructure. This is deeply concerning.

“In the past few days, [Brexit Secretary] David Davis has said he can 'live with' a transition period of under two years if it helps to secure an early deal.

"But even this time could prove to be too short to conclude a comprehensive agreement. Given the modelling we have seen, a 'no deal' scenario is a significant danger to the UK.”

But Tory vice chairman John Whittingdale said the report was “far too negative” and unsupported by evidence the committee heard.

He said: “The recommendations essentially ignore the wishes of the people and would delay Brexit by an indefinite period.

“This disrespects the Referendum result, and it ignores the manifesto commitments of the parties pledged to honouring it.”

Tory MP Jacob Rees-Mogg, chair of the pro-Brexit European Research Group, added: “The Committee’s majority report is the prospectus for the vassal state.

“ It is a future not worthy of us as a country, and I am sure that Theresa May will rightly reject a report by the High Priests of Remain.

“The majority report would keep us in the Customs Union and the Single Market which is an attempt to keep us in the EU by sleight of hand. Those of us who respect the instructions the people gave us in the Referendum could not support so partisan a text.”

SNP MP Peter Grant, who is on the Brexit Committee, added: “The report lists a catalogue of failures to provide any kind of certainty on citizens' rights, on trade, on the Irish border, and on almost everything else related to Brexit.

“Twenty-one months on from the EU referendum and with barely six months before the proposed Brexit date, the UK government still has nothing in place.”

In a speech in London today, LibDem leader Sir Vince Cable will say the Salisbury nerve agent shows the “utter folly” of Brexit when solidarity with European allies is needed.