France’s president, Emmanuel Macron, has said he wants to avoid Brexit “polluting” the EU after 31 October, and that European leaders need to know when the UK’s prolonged departure will come to an end.

In April, Macron stood alone at a meeting of the EU27 in championing a short Brexit extension in opposition to those willing to give the UK until next year to complete its withdrawal.

The October deadline for the British government to have ratified the withdrawal agreement or face a no-deal exit was a compromise position brokered with the German chancellor, Angela Merkel.

Macron, in a sign of the frustration in Brussels at the risk posed to its future agenda by the UK’s continued membership, told the Belgian newspaper Le Soir the EU needed a clear end date to the continuing saga.

The French president, who is running behind Marine Le Pen in polls of voting intentions in this weekend’s European elections, said: “In the case of Brexit, you just have to know at some point whether it stops or not.

“If we follow the logic of saying that it scares us and that we are prepared not to respect the British vote, we betray both the British and the interest of the British.”

Macron added: “That’s why I spoke. But I did not try to act alone. If I had wanted, the French veto would have been enough to block unanimity. We have, with [the Belgian prime minister] Charles Michel and Chancellor Merkel in particular, built a consensus around 31 October, that is to say before the establishment of the new [European] commission, to prevent the next mandate being polluted by this subject we’ve been talking about for three years.”

The EU’s leaders could be faced with the question of whether to extend the UK’s membership of the bloc once again in the autumn, but there are growing concerns that UK MEPs’ presence in the European elections will undermine its credibility as an EU institution.

A strong vote for Labour would bolster the socialist group but there would be questions over whether it would be appropriate for them to use that mandate in negotiations over top EU jobs given the UK’s expected exit.

Macron said, however, that he was not convinced by the spitzenkandidaten system under which the nominated candidate of the largest group in the European parliament would become the European commission president.

The German MEP Manfred Weber, who has not had any experience of national government, is the candidate for the centre-right European People’s party (EPP), but Macron suggested that others, including the EU’s chief negotiator, Michel Barnier, would be in the running.

Macron said: “I do not feel committed to the system of spitzenkandidaten. There are leaders among these candidates who have the qualities. There are also leaders around the [European] council table who can claim it. It will be a question of balance the next day, and of ability to build a consensus between us.

“In my opinion, experience at the highest level of government or the European commission is undeniably an important criterion. A more or less long experience because I want all generations to be represented …

“But undeniably, Michel Barnier is a man who has great qualities and he has demonstrated it again in the way of managing the negotiations with the British. He is therefore one of the European leaders who have eminent qualities and who can be part of this list.”