Jonathan Faull, the most senior European Commission civil servant in charge of financial regulation, is to leave the Directorate-General for Financial Stability, Financial Services and Capital Markets Union (DG FISMA) at the beginning of September.

Part of a wide-ranging reshuffle of directors-general within the Commission, Faull is to head up a new directorate overseeing issues relating to the UK’s referendum on its European Union membership.

Olivier Guersent, currently Faull’s deputy at DG FISMA, is to succeed him when the changes take effect from 1 September.

Faull has worked for various European institutions for decades, starting within the department responsible for competition in 1984.

Over the next 15 years, he held a number of senior roles within DG Competition, eventually becoming deputy director-general responsible for state aid cases in 1999.

He was Commission spokesman for four years during the presidency of Romano Prodi but then was promoted to director-general of DG Justice.

In 2010, he was named the most senior civil servant at the directorate-general for internal market, headed by commissioner Michel Barnier, and retained his position when it was reshaped into DG FISMA under current president Jean-Claude Juncker.

Guersent has worked for the French government and competition authority before joining the Commission in 1992, working within a number of commissioners’ private offices and directorates-general.

He has been Faull’s deputy since the summer of 2014.

The UK Conservative government won the election in May promising to offer an in/out referendum on EU membership by 2017.