Slaughter and May competition partner Sarah Cardell is set to leave the firm to take up a role at energy watchdog Ofgem.

Cardell (pictured) is due to join Ofgem next month as partner for legal markets, after three years as a partner at Slaughters.

Her appointment comes after the energy regulator's joint legal director Duncan Sinclair resigned last year to return to the Bar. He joined 39 Essex Street in October 2010.

Cardell, who is currently on maternity leave from Slaughters, has worked with clients including the European Commission, the Office of Fair Trading, BHP Billiton, Thomas Cook, Centrica and BUPA while at the magic circle firm.

Slaughters practice partner Paul Olney said: "We're obviously sad that Sarah is going. It is rare for partners to leave us and usually quite specific to their own personal circumstances.

"The Ofgem position will be a fascinating challenge for Sarah but as an outstanding competition and regulatory lawyer I'm sure she will rise to it."

Slaughters' competition practice has seven partners following Cardell's departure, with five in London and two in Brussels.

In December corporate and finance partner Lucy Wylde left Slaughters to take up a position as general counsel of HM Treasury arm the Asset Protection Agency.

She had been on secondment to the Treasury since March 2009, serving as the agency's GC since its launch in December that year.