PM tells senior MPs talks with EU would have to be reopened if UK sought extension to departure process • Follow the latest political news - live updates

The government would have to reopen negotiations with the EU on the Brexit deal if it sought an extension to the departure process to allow for a second referendum on the plan, Theresa May has told a committee of senior MPs.

Asked whether an extension could be made to article 50, the timetable which decrees the UK leave on 29 March next year, to allow time for a referendum, May argued this would invalidate the deal agreed in Brussels on Sunday.

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Appearing before the liaison committee, which groups together the chairs of various subject-specific Commons committees, the prime minister also insisted a no-deal departure was still possible if MPs voted down her plan, despite forecasts it could severely hit the economy and affect the supply of medicines.

Answering questions from Sarah Wollaston, the Conservative MP who chairs the health committee, May rejected the idea of a second referendum, saying it would both affect “the integrity of politicians and people’s trust in politicians” and would bring practical complications.

“There’s a paradox here,” May said. “To extend article 50, actually, you’re then in the business of renegotiating the deal. This is the point. The deal is the deal at this point in time.”

Pressed on whether this was the case, May reiterated the argument: “What is clear is that any extension to article 50, anything like that, reopens the negotiations, reopens the deal. And at that point the deal can go, frankly, in any direction.”

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But asked by Wollaston whether the EU had directly told her this, May dodged the question, saying: “What has been made clear is this is the deal that we have negotiated with the European Union.”

She added: “I think the most important reason why we should not be going down the route of a second referendum is that we asked the British people, they’ve given us their view, and we should deliver on that view.”

Wollaston ended by saying that agreeing Brexit without a new vote was “like wheeling someone into the operating theatre based on a consent form they signed two years ago without really knowing what the operation was”.

May rejected this, saying a new referendum would create “a period of more uncertainty and more division”.

Many of the questions in the 90-minute session focused on the impact of a no-deal departure given the dire economic forecasts of what it would bring, plus concerns about supplies of medicines and other medical supplies.

May repeatedly declined to rule it out as an option, indicating that if it did happen it would be the responsibility of MPs who voted down her deal.

Wollaston asked May: “There are so many patients that will face very serious disruption to essential supplies and medicine – is that keeping you awake at night?”

The prime minister replied: “They are looking at what is necessary were it the circumstance of a no deal. But of course the way to ensure that we get a good deal and we are able to see that smooth and orderly exit is to ratify the deal that the government has ratified.”

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Wollaston pressed May, asking if a responsible government could “allow the scale of chaos that would ensue if we had no deal and no transition period”.

May replied: “I think the role of a responsible government in these circumstances is to ensure that government is prepared for all scenarios that develop and to ensure that where there are potential difficulties that those are mitigated to the greatest extent possible.”

Under earlier questioning about a no deal from Labour’s Rachel Reeves, who chairs the business committee, May also placed the responsibility on MPs.

The prime minister said: “If the house was to vote down the deal that has been agreed, given that the European Union has been clear this is the deal that has been agreed, and this is the deal that is on the table, then obviously decisions would have to be taken.”

Pressed on this, May said: “The timetable is such that actually some people would need to take some practical steps in relation to no deal.”