EU 'must lift lid' on secretive 'deal-making'

"However, discussions between the co‐legislators behind closed doors—without adequate documentation being made publicly available—risk the creation of public suspicion and uncertainty, and may hinder informed debate about its content," she wrote.

The meetings, known as trilogues, have helped to speed up the legislative process at the cost of transparency.

According to the ombudsman, 85 percent of legislation concluded in the last term of parliament (2009-2014) was done through trilogues. Only two terms earlier, that percentage was just 29 percent.

Although some information may be available on the meetings, it is often dispersed and difficult to find.

"This, regrettably, increases the ‘mystique’ of trilogues, discouraging citizens from engagement and thus diminishing their democratic rights," wrote the ombudsman.

A piece of legislation, after being proposed by the European Commission, has to be approved by the European Parliament and the Council of the EU, where member states meet.

But the parliament and council often want to change different parts of the legislation, which means it would take several readings to reach a compromise situation. Instead, they thrash out deals behind closed doors.

O'Reilly called on the European Commission, European Parliament, and Council of the EU to create one common database in which citizens can find dates of the meetings, compromise texts and a list of names of people who took part.