The City of London Corporations special representative to the EU Jeremy Browne is stepping down after three years with the organisation.
Browne, who had been tasked with championing the City's call for mutual recognition as part of the Brexit process, will leave at the end of August.
It is not clear whether the role is being disbanded or whether he will be replaced.
Policy Chairman Catherine McGuinness thanked Browne for his "invaluable" work, adding: “Jeremys work has been pivotal over the last three years – particularly following the UKs decision to leave the European Union.
“He has generated a clearer understanding of the climate across Europe at this critical time, and helped the City Corporation build stronger, more tangible relationships with member states."
Browne said: "I am confident that the City will continue to be the worlds pre-eminent financial centre and a major asset for the wider European economy. It remains a valuable objective to develop a mutually productive relationship with our own continent as well as ensuring that we are attractive to dynamic businesses and talented people.
“The City Corporation has been at the forefront of establishing a new working partnership with the EU and its engagement will continue to be vital going forward.”