The chances of the UK staying in the EU are as high as 30% as the country would be likely to reject Brexit in a second referendum, the president of the European council, Donald Tusk, has said.

The bloc’s most senior official claimed the British public had only truly debated Brexit after the 2016 referendum and there was significant reason to believe the leave vote could be reversed.

Describing the decision by the former British prime minister, David Cameron, to call the vote as a political miscalculation, Tusk said he would expect a different result in a vote today given what had been learned about the consequences of leaving.

“The referendum was at the worst possible moment, it is the result of a wrong political calculation,” Tusk said in an interview with the Polish newspaper Gazeta Wyborcza (GW) that was shared with the Guardian as part of the Europa collaboration of six European newspapers.

“A real debate about the consequences of Brexit wasn’t had during the referendum campaign, but only after the vote. Today the result would probably look different. Paradoxically, Brexit awoke in Great Britain a pro-European movement.”

Tusk, whose tenure as president of the European council, the EU body made up of the 28 leaders of member states, is due to end in November, said he had been moved by the anti-Brexit march in London earlier this year during which he was celebrated as a voice calling for the UK to reconsider.

While suggesting there was a “crisis in leadership” among remainers, in an echo of his previous claim that the Labour party under Jeremy Corbyn is essentially pro-Brexit, Tusk said he still believed it was possible the question could again be put to the people.

The Labour leader this week suggested a second referendum could be a “healing” development, as cross-party talks over the Brexit impasse in Westminster appeared to be fizzling out.

“Hannah Arendt said that in politics and history things only become irreversible when people recognise them as such. Because, in themselves, they are not irreversible,” Tusk said.

“After the British referendum in 2016, I thought that if we recognise that the case is closed, it will be the end. Today the chance that Brexit will not happen is, in my opinion, 20-30%. That’s a lot.

“From month to month, it is becoming increasingly clear that the UK’s exit from the EU will look completely different than the Brexit that was promoted,” Tusk added. “I see no reason to capitulate.”

The former Polish prime minister, who was interviewed by the GW editor, Adam Michnik, to mark the newspaper’s 30th anniversary, said there was historical precedent for the British people revisiting decisions made in referendums.

“Even if we repeat that the referendum is the expression of will by the nation, and the will of the nation must be respected, yes, you have to respect it,” he said. “But the 2016 referendum was not the first on the UK‘s membership of the EU. The first took place in 1975, when the British, two years after entering the European Economic Commmunity, decided whether to remain in it.

“If the 2016 referendum was able to change the result of the referendum in 1975, why can it not be changed again? Nothing is irreversible until people believe it is.”

In April, Britain’s membership of the EU was extended to 31 October by the 27 heads of state and government to allow Downing Street more time to secure ratification of the withdrawal agreement.

The UK had been due to leave the bloc on 29 March, after two years of negotiations, but the repeated rejection of Theresa May’s Brexit deal by the Commons forced the prime minister to seek more time.

Tusk admitted that “almost every day” he heard from those who said the UK should be cut off from the EU if it was unable to come to a deal.

“My main task is to make sure that the EU has shown patience despite being felt in many places on the continent these negative emotions,” he said. “I say to colleagues to wait a while longer. For now, we managed to win some time. The deadline expires in October, but I will persuade them – if necessary – not to close the calendar. There is no place for rush to Brexit. Churchill used to say that a problem postponed is partially solved.”