The EU Commission is being investigated over a secret group chat involving Ursula von der Leyen, Volodymyr Zelensky and several European leaders that discussed how to deal with Donald Trump, according to reports.

The group is said to have included UK prime minister Sir Keir Starmer, French president Emmanuel Macron, German chancellor Friedrich Merz and Italian prime minister Giorgia Meloni.

But the contents of the chat have remained private, after the EU Commission rejected calls by a media company to provide access to the correspondence.

Ombudsman Teresa Anjinho said in a letter to Ms von der Leyen last Friday that she would open an investigation into the handling of the request to determine whether the Commission had shown a lack of transparency.

Dutch investigative organisation Follow the Money requested access to the correspondence in January, but this was rejected by the Commission on the basis that publication could damage the EU’s relations with countries not in the bloc.

The investigation is expected to take a number of months, with a meeting between representatives for the Commission and Ms Anjinho not scheduled until mid-July.

In the initial decision to refuse access to the group chats in early March, the Commission said there had been “permanent informal and personal contact with the Heads of State and Government of third countries and the Member States, orally and in writing”. It said access to these exchanges was not in the public interest.

The complainant later argued the Commission had not sufficiently explained its refusal to grant access. In response, the Commission again refused access on the basis of an “exception relating to the protection of the public interest as regards international relations”.

In that response on 20 May, the Commission did not give a position on whether the exchanges on the group chat constitute documents that it officially holds or not.

The complainant afterwards turned to the ombudsman, arguing that the Commission did not carry out an assessment of the requested documents and had not looked at the possibility of granting partial, rather than full access.

He argued the Commission had not evidenced any concrete harm caused by releasing the exchanges, and had offered no information regarding the existence, possession and retention of the messages.

The ombudsman has also requested all documents from the Commission which fall within the scope of the complainant’s access request.

Politico first reported on the so-called ‘Washington Group’ in January, with a source revealing that the leaders would message whenever Trump did or said something potentially damaging.

“When things start moving quickly, it’s hard to do the coordination, and this group [chat] is really effective,” a source familiar with the arrangement told the outlet. “It tells you a lot about the personal relationships and how they matter.”

The group, described as “informal but active”, was arranged after the European leaders visited the White House along with Zelensky last August.

European leaders were initially careful not to anger Trump when he began his second term in January last year for fear of provoking his anger, but have since become more bold in publicly criticising him. Macron and Merz, in particular, have vocally opposed his war in Iran.

Earlier this year, a diplomatic row broke out after several European leaders spoke disparagingly of Trump administration officials on a group call.

Macron told European leaders in a conference call that Trump could “betray” Ukraine by forcing it to give up territory “without clarity on security guarantees”, Germany’s Der Spiegel newspaper reported.

In comments that appear to refer to Trump envoys Steve Witkoff and Jared Kushner, German chancellor Merz said: “They are playing games, both with you and with us.”

The Finnish president, Alexander Stubb, who enjoys a warm relationship with Trump, said: “We must not leave Ukraine and Volodymyr alone with these guys.” Nato secretary general Mark Rutte concurred, saying: “I agree with Alexander – we must protect Volodymyr.”

The Independent has contacted the European Commission for comment.