A judge opened a criminal inquiry while Jean-Claude Juncker was meeting Theresa May for Brexit talks in Brussels Yves Herman/ Reuters

The president of the European Commission is embroiled in a new criminal investigation into claims that “tampered” evidence misled an inquiry into phone-tapping.

Jean-Claude Juncker faces accusations that his officials presented inaccurate information under oath in a case involving an alleged illegal wiretap more than ten years ago when he was prime minister of Luxembourg.

The Times has learnt that last week, as Mr Juncker met Theresa May for Brexit talks in Brussels, a Luxembourg judge opened a criminal inquiry into whether officials working for Mr Juncker were responsible for an incomplete transcript of a covertly recorded conversation, which may have disguised his alleged role in phone-tapping.

The inquiry means that Mr Juncker, 63, risks being caught up in a scandal that threatens his reputation…