By Carla Mozee, MarketWatch

LONDON (MarketWatch) -- U.K. stocks seesawed Friday, with utility shares losing ground on the FTSE 100 as the benchmark moves toward a weekly loss.

The FTSE 100 darted between gains and losses, and recently shed 2 points at 6,758.56. It's on track for a weekly loss of 2.2%, which would be its biggest weekly decline since December.

Shares of energy provider SSE PLC fell 1.3% as did British Gas' parent company Centrica PLC as Labour Party leader Ed Miliband is expected to say that if his party wins the May 7 election that he'll push for legislation allowing the energy regulator to force companies to cut prices by up to 10% if it's determined they are too high.

Miliband is slated to outline the plan at a Labour Party event on Saturday in Birmingham, according to reports.

Also moving lower were shares Diageo PLC , losing 1.6% after the spirits maker was downgraded to underperform from neutral at Credit Suisse.

But advancers were led by a 2% rise in Whitbread PLC , after a ratings upgrade at Deutsche Bank to buy from hold for the company behind Costa Coffee and the Premier Inn hotel chain.

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