Dominic Raab has been forced into an embarrassing climbdown after appearing to suggest that the UK’s increasingly fraught Brexit negotiations with the EU could be completed in three weeks’ time.

The Brexit secretary admitted there was “no set date for the negotiations to conclude” three hours after a letter he had sent to a select committee was released in which he said he was happy to appear before it on 21 November after “a deal is finalised”.

Once thought a safe pair of hands to take over the negotiations after the resignation of David Davis, Raab’s personally signed correspondence briefly caused the pound to rise and raised questions in Brussels.

The subsequent retreat prompted his shadow, Sir Keir Starmer, to conclude that he had been forced to execute “one of the quickest U-turns in political history”.

The suggestion that a keenly awaited deal was close was contained in a surprisingly optimistic three-page letter dated 24 October to the Brexit select committee, which was released earlier on Wednesday afternoon.

Raab was responding to a request to appear in front of MPs, and told its chairman Hilary Benn that he would be “happy to give evidence when a deal is finalised, and currently expect November 21 to be suitable”.

With no sign of a breakthrough in the Brexit negotiations, the timetable appeared optimistic but theoretically possible. Sterling rose by 0.5% on the foreign exchanges during the afternoon.

A surprised No 10 was quick to downplay the significance of the date, and said it was not aware of Raab’s letter before it was released because it was not considered important. “We hope to reach an agreement as soon as possible,” the prime minister’s official spokesman said.

Two and half hours later, a spokesperson for the Department for Exiting the European Union confirmed there was no significance to the remarks in the letter: “There is no set date for the negotiations to conclude. The 21st November was the date offered by the Chair of the Select Committee for the Secretary of State to give evidence.”

Downing Street sources are still indicating in private they hope the Brexit talks will be concluded in November, although the two sides are yet to agree on the appropriate backstop to ensure a free-flowing land border in Ireland and how that backstop could be wound up.

The UK wants the EU to agree to drop the Northern Ireland-only backstop in favour of allowing the entire UK to remain in a country-wide “temporary customs arrangement” with the 27-country bloc if no free trade deal can be concluded by the time the transition period ends in December 2020.

Once a deal is deemed near to completion by officials from the UK and the European Union, a special European summit will be convened to reach an agreement. It will then have to be ratified by MPs, although it continues to be unclear if Theresa May will be able to force her deal through parliament.

Davis said that while he believed the PM will get a deal with the EU, “anything based on the Chequers plan [in which the UK would retain a common rule book for food and goods after Brexit] or one that keeps us in the customs union will not pass the Commons”.

Others are hoping to propose alternatives to May’s final deal in the Commons, although the clerk of the House of Commons, Sir David Natzler, told MPs that the government could ignore the result of votes passed unless they were carried as amendments. Natzler said “there’s not statutory obligation” for May to act if MPs were to vote in a motion for a second referendum.

EU prepares for a no-deal Brexit amid lack of progress on talks Read more

Shortly after the Raab letter emerged, EU ambassadors for the 27 member states were told on Wednesday that “nothing new” had emerged from recent contacts with Downing Street’s Brexit adviser, Olly Robbins.

Sabine Weyand, the EU’s deputy chief negotiator, told diplomats that they are in the “final stretch on the backstop talks” and “nothing has changed, there are no new ideas”. One EU diplomat added: “The negotiations are around the same concept.”

The EU is continuing to insist that the Northern Ireland specific backstop, under which the province could remain in the single market and customs union, must stay in the withdrawal agreement, even if there is also a commitment to negotiate an all-UK customs union during the transition period.

The prime minister has repeatedly said that this would be unacceptable. By contrast, Raab’s letter to the select committee suggested that EU has accepted the idea of the temporary customs arrangement. “We agree on the principle of a UK-wide customs backstop,” the Brexit secretary wrote.

On Wednesday afternoon May addressed around 150 chairs and chief executives of UK businesses and business group leaders about progress in the Brexit negotiations and Monday’s budget, and sought to encourage them to support whatever deal she brings back from Brussels.

A European commission spokesman declined to comment on the next steps in the talks, only confirming that “contacts continue on a technical level”.

Ireland’s deputy prime minister Simon Coveney said it was still possible that a Brexit deal could be done by 21 November but it would mean the British team removing “the remaining barrier” over the Irish backstop. He said that he had “frank and very long discussions” with the foreign secretary, Jeremy Hunt, on Wednesday morning and the Brexit secretary on Tuesday night.

“I think it is possible to get a deal in November, he said. But he warned there would “not be a new EU leaders’ summit on Brexit if there is not a signal from the negotiating teams that there is something for EU leaders to sign off on.”

EU prepares for a no-deal Brexit amid lack of progress on talks Read more

He said that if an emergency EU summit was to go ahead in mid-November, “a signal would need to come from the negotiating teams next week to be able to put the machinery in place for an EU summit in November”.

Earlier, senior EU officials had said that if Raab’s timescale was real it would have required an “urgent” breakthrough on the backstop issue, with an agreement on paper well ahead of any Brexit summit in the middle of November.

EU sources added, however, that the timings were tight and the UK government needed to be realistic about the period that would be needed for the heads of state and government to assess the situation ahead of a crunch summit. The two negotiating teams are due to go into “the tunnel” of confidential talks next week.