General Secretary of the European Commission Martin Selmayr (R), sits European Commission President Jean-Claude Juncker ahead of a debate on the guidelines on the framework of future EU-UK relations at the European Parliament in Strasbourg, France, March 13, 2018. REUTERS/Vincent Kessler

BRUSSELS (Reuters) - The European Parliament’s budgetary control committee wants a senior EU Commission official to clarify the sudden promotion of its president’s chief aide to the top of the EU civil service, underlining the continuing unease among lawmakers over the move.

European Commission President Jean-Claude Juncker elevated Martin Selmayr, a 47-year-old German, to be secretary-general of the EU body last month, triggering accusations from Brexit campaigner and MEP Nigel Farage of nepotism, from others about a lack of transparency and complaints to the European Ombudsman.

The saga may weaken the Commission’s power to get wayward EU countries to toe the line. Hungary, criticized by the Commission of weakening democratic checks and balances, has accused the agency of double standards.

The Greens bloc in the European Parliament has threatened to hold up approval of the Commission’s budget over the issue while the Liberals want the promotion reversed.

Juncker, whose five-year term ends in October next year, has defended the appointment as one he and his 27 fellow commissioners are entitled to make, as well as on the basis of Selmayr’s capabilities.

However, diplomats say member states have begun to worry that the issue was becoming an unwelcome distraction and could even fuel eurosceptics before EU elections next year.

The committee, which is made up of 30 lawmakers from 17 EU countries and checks how EU funds are used, said on Monday that it planned to ask EU budgetary chief Guenther Oettinger for more details at a public hearing on March 27.

They have also written to Juncker for more information.