Freshfields Bruckhaus Deringer and Slaughter and May are advising on the merger of energy giants Npower and SSE's domestic retail operations.

The deal will create a new independent British retail energy company, listed on the London Stock Exchange. Npower parent company Innogy will own 34.4%, with SSE shareholders holding the other 65.6%.

Freshfields, which was appointed to SSE's inaugural legal panel in 2014, is advising the Scotland-based company with a team led by London corporate partner Simon Marchant, alongside fellow corporate partners Julian Pritchard and Andrew Craig, and competition partners Deidre Trapp and  James Aitken.

Slaughters and Hengeler Mueller are advising Innogy, working with the Germany company's in-house legal team.

Slaughters corporate partners Richard Smith and Tim Boxell are leading the magic circle firm's team alongside competition partner Lisa Wright, financing partner Ed Fife and pensions and employment partners Charles Cameron, Padraig Cronin and Daniel Schaffer.

The Slaughters team also includes intellectual property partner Rob Sumroy, tax partner Gareth Miles and financial regulation partner Nick Bonsall, while the Hengeler team is being led by corporate partners Andreas Austmann and Thomas Meurer.

Innogy's in-house team includes Innogy GC Claudia Mayfeld, head of legal M&A Tobias Bage and head of legal antitrust and energy Malte Abel.

Other firms appointed to SSE's panel in 2014 alongside Freshfields included Addleshaw Goddard, Osborne Clarke, CMS and Kennedys.

In 2015, Freshfields' Trapp advised SSE over market reforms following a damning report by the Competition and Markets Authority, which found that energy companies were overcharging customers who failed to switch suppliers.