The utility's wholesale division, which includes its power plants and gas production, posted an 83 percent fall in operating profit to 26.7 million pounds for the half year ended Sept. 30, due to lower generation at its thermal power stations and wind farms.

SSE said it expected full-year EPS to be the same level as the previous year's 123.4 pence. The downgrade weighed on its shares, which fell 2 percent by 09:47 GMT.

Britain's competition watchdog is investigating the entire energy supply market, a probe that could lead to the break up of some of the country's largest energy providers.

"(SSE's) cautious tone is not that surprising, given the ongoing Competition and Markets Authority (CMA) investigation into energy supply," said Whitman Howard Utilities Analyst Angelos Anastasiou.

Britain's energy suppliers have come under political pressure for squeezing consumers' pockets by increasing prices. In response SSE has pledged not to raise its tariffs until 2016.

But SSE lost 210,000 customer accounts in Britain and Ireland between April and September as more users switched to cheaper independent suppliers.

SSE said it was on track to make disposals totalling 1 billion pounds, of which around 400 million have already been signed.

The energy firm has invested in wind power but analysts said this 6 billion-pound commitment was not delivering suitable returns as weak power prices were eating into margins.

"SSE's big bet in recent years has been on wind power... (but) it will certainly not be a driver for earnings growth," said analysts at Liberum.

(Reporting by Karolin Schaps; editing by Sarah Young and Louise Heavens)