FRANKFURT (Reuters) - RWE (>> RWE AG) warned it would only barely reach its full-year net profit target as persistent problems at its British business pile pressure on Chief Executive Peter Terium to come up with a convincing turnaround plan.

Germany's second-biggest utility said on Thursday it still expected to achieve adjusted net income of 1.1-1.3 billion euros (789-920 million pounds) in 2015, "even if only just".

Apart from a structural crisis that has gripped the German power sector, RWE has also suffered from increased competition and billing problems in Britain, where its npower business swung to an operating loss of 66 million euros for the first nine months.

"Substantial customer losses and billing problems are not good for RWE's reputation, but we are working hard to deal with these difficulties and find a solution," Terium wrote in a letter to shareholders.

Terium has defended his decision not to follow larger peer E.ON (>> E.ON SE) in breaking up the company, but he is under mounting pressure to turn around the 117-year old utility. Its shares have halved in value since the beginning of the year.

RWE's nine-month operating profit fell 9 percent to 2.65 billion euros, slightly higher than the 2.59 billion average analyst estimate, driven by better than expected earnings at its renewables unit Innogy.

(Reporting by Christoph Steitz; editing by Tom Pfeiffer)

Stocks treated in this article : RWE AG, E.ON SE