The UK energy giant BP has reported a sharp fall in earnings and cut its full-year oil and gas output forecast for the third time in less than two months.

Commerzbank analyst Steve Turner said it was "very disappointing".

BP's earnings fell 13% during the July to September period and its net profits came in at about $3bn (�2bn) - well below analysts' expectations.

BP shares fell 7.2% to close at 392.5p, the first time the stock has slipped below �4 for four years.

Weak growth

The world's second largest energy group now expects output to grow by just 3% this year, below its 5.5% long-term target.

Earlier this month, in the group's latest trading statement, BP predicted growth would come in at 4%.

In August, BP was still clinging to its prediction of 5.5% output growth this year.

Output growth is widely seen as a sign of success among oil companies at a time when oil prices are historically high.

BP said the months ahead could prove difficult.

"The current environment has little upside and significant downside risks," said chief executive Lord Browne.

New finance chief

Stepping in to oversee BP's finances ahead of what is expected to be a difficult period for the group will be Byron Grote, currently in charge of BP's Asian interests.

Mr Grote will replace chief financial officer John Buchanan on 21 November following his retirement.

Oil industry shares slipped across the board because of fears that BP's rivals Royal Dutch Shell and Exxon Mobil will reveal similar difficulties when they reveal their latest financial figures later this week.