Innogy, which was originally carved out from RWE in 2016, said that competition in the power retail market continued to be fierce, adding it lost 557,000 electricity and gas clients across Europe since the start of the year, mainly in Britain.

E.ON, too, warned of ongoing competition in the retail segment earlier this week, particularly in Britain, where the government last month agreed on a price cap. E.ON will take over Innogy's client portfolio as part of the break-up.

Innogy's first-half adjusted earnings before interest and tax (EBIT) fell to 1.55 billion euros ($1.79 billion), slightly below the 1.59 billion average forecast in a Reuters poll of banks and brokerages.

Shares in the company, which builds and operates wind farms, power and gas networks and has 22 million power and gas clients across the continent, were indicated to open 0.5 percent lower at 0547 GMT.

E.ON, Germany's largest energy group by market value, last month said it had secured a stake of 86.2 percent in Innogy, which will be transferred once the complex transaction closes next year.

(Reporting by Christoph Steitz; Editing by Edward Taylor)