Sir Stephen Sherbourne will take over from Andrew Dunlop, who founded the company as Politics International in 1991 and is now leaving to pursue other interests.
Sherbourne is well known in political circles and throughout the public affairs industry, having been on both sides of the fence. From 1983 to 1988 he worked for Thatcher as head of the prime minister's political office.
More recently, from 2003 to 2005, he was chief of staff to Conservative Party leader Michael Howard. He is also a former director of Chime Communications and chairman of Bell Pottinger Public Affairs.
Despite joining Interel, Sherbourne is expected to continue as a non-executive director at financial PR firm Smithfield.
Interel has offices in Brussels, Berlin, London, Paris and Prague. Earlier this year, the UK arm was subject to a management buyout by more than 20 staff members.
Clients include Expedia, SABMiller, PayPoint, Saab, Virgin Money and McAfee.