BP starts North Sea gas field expected to add 3 pct to UK output

* Output to peak at 100 mscf/d in 2013

* 430 bscf estimated in place at gas field

LONDON, Oct 4 (Reuters) - Britain's gas production is set for a three percent boost next year from current levels after BP's Devenick North Sea gas field started production on Thursday, Energy Minister John Hayes said.

Output from the field will peak at up to 100 million standard cubic feet per day (mscf/d) in 2013 and production is expected until 2025, BP said.

"When the Devenick project comes on full stream it will add an extra three percent to current UK gas production, enough to supply the equivalent of more than half a million homes a year," Hayes said in a statement.

BP and RWE Dea , which owns 11.3 percent of the field, spent 650 million pounds ($1.04 billion) on the project, where appraisal well drills between 1986-2001 indicated around 430 billion scf of gas was in place at the site.

UK domestic oil and gas production could increase this year after its worst annual decline since the 1960s, Haye's predecessor said in an interview last month.

Overall, British fossil fuel output is expected to decline in coming years, extending the UK's dependence on imported oil and gas.

($1 = 0.6222 British pounds)

(Reporting by Karolin Schaps; editing by Jason Neely)

((karolin.schaps@thomsonreuters.com)(+440207 542 6622)(Reuters Messaging: karolin.schaps.reuters.com@reuters.net))