The president of the European Commission has said he would like Britain to rejoin the European Union after Brexit – using the little-known treaty clause “Article 49”.

Speaking at the European Parliament in Strasbourg Jean-Claude Juncker said “the exit of Britain is a catastrophe” and suggested he would like the country to stay.

But Mr Juncker added for the first time in public that even once Britain had left, it could still change its mind and return to the bloc by invoking another treaty clause.

“Once the British have left under Article 50 there is still Article 49 which allows a return to membership and I would like that,” he told MEPs. “I would like us now to treat each other with respect and not abandon each other.”

Mr Juncker on Tuesday had endorsed a statement by European Council president Donald Tusk suggesting that Britain could still “change its mind” to leave, telling the British people that “our hearts are open to you”.

“Mr Tusk and I once again reached out to the British government yesterday and said that if the British people, the British parliament, the British government, wish for another way than Brexit, we would be prepared to discuss it. We are not throwing out the British, we want them to stay,” he explained.

And if they want to, they should be able to. But I noticed that in London, they have reacted almost upset at this reaction. Be it as it may, once the British have left under Article 50 there is still Article 49 which allows a return to membership and I would like that. I would like us now to treat each other with respect and not abandon each other.”

In March 2017 Theresa May triggered Article 50 of the Treaty of the European Union, formally beginning the two-year legal process of Britain’s exit, which is set to conclude in March 2019.

Article 49 is the normal way for a European country to join the union – a process that normally takes years. Any new member state requires the unanimous consent of the 27 member states on the European Council, the consent of the European Parliament, and consultation with the Commission.

Brexit: the deciders Show all 8 1 /8 Brexit: the deciders Brexit: the deciders European Union's chief Brexit negotiator, Michel Barnier Getty Brexit: the deciders French President Emmanuel Macron Getty Brexit: the deciders German Chancellor Angela Merkel Reuters Brexit: the deciders Commission President Jean-Claude Juncker EPA Brexit: the deciders The European Parliament's chief Brexit negotiator Guy Verhofstadt Getty Brexit: the deciders Britain's Prime Minister Theresa May Getty Images Brexit: the deciders Britain's Chancellor of the Exchequer, Philip Hammond PA Brexit: the deciders After the first and second appointed Brexit secretaries resigned (David Davis and Dominic Raab respectively), Stephen Barclay is currently heading up the position PA

It is unclear whether the EU would grant Britain its opt-outs and budget rebates were it to rejoin in this manner.

Polling suggests there has been little movement in how people would vote in a second EU referendum, were one called – with the results likely to be similar to the vote held in 2016.