George Eykyn (above), director of comms for Centrica brand British Gas, had joined the company in February 2014 following a career in Government, latterly at DCLG.
Outgoing director of UK and EU Policy Katherine Mercer, has been with the firm for 16 years.
Lisa Poole, Centrica's director of public affairs and policy, is leaving after 12 years at the firm.
Eykyn told PRWeek he was still to confirm his next move. He said of his time at Centrica: "The pressures in the sector have never been greater and it's been an extremely interesting time. I'm really pleased to be leaving the excellent comms team in good shape as I move on to my next challenge."
It is not known what Mercer or Poole will do next.
In March last year, John Moorwood was appointed as UK and Europe corporate affairs director for Centrica, following nearly a decade at payday lender Wonga. He reports to group corporate affairs director Nick Baird, whose global role means he also oversees teams in the US and Canada.
During 2016, Moorwood's predecessor Christine McGourty implemented a change under which the previously separate comms functions for British Gas and Centrica were combined. McGourty's 15-month tenure ended in March 2017 when she moved to electronics firm Laird.
Moorwood now has five direct reports, including director of media relations Tim Cowen and deputy head of corporate comms and policy William Heald.
Centrica's main agencies are Weber Shandwick, which has run consumer and trade PR for two years; corporate and financial PR advisers Brunswick and regional PR support agency Citypress. Connect Communications is also used for public affairs projects.