By Kit Rees
LONDON (Reuters) - A drop in Centrica's <CNA.L> shares after a trading update weighed on the blue chip FTSE 100 <.FTSE> on Thursday, while housebuilders recovered some ground.
Britain's blue chip FTSE 100 <.FTSE> index was down 0.3 percent at 7,397.51 points by 0947 GMT, giving up the previous session's sterling-driven gains.
Centrica <CNA.L> was by far the biggest faller, down more than 16 percent and on track for its biggest one-day loss since listing in 1997 after the utility gave a trading update, missing earnings expectations.
Centrica said that it had lost 823,000 energy supply customers in four months.
"2017 is on track to be another tough year for Centrica," analysts at Jefferies said in a note.
Jefferies analysts flagged weakness in Centrica's North America and UK business.
Shares in utility peers National Grid <NG.L> and SSE <SSE.L> also declined 3.2 percent and 2.4 percent respectively.
While the utilities sector was the biggest weight on the top share index, falls among financials and more defensive sectors such as telecoms and consumer staples also dragged the index lower.
Sage Group <SGE.L> was the biggest gainer, up 2.7 percent after several brokers upped their price targets for the stock.
Housebuilders recouped some of the previous session's losses, with Berkeley Group <BKGH.L>, Barratt Developments <BDEV.L> and Taylor Wimpey <TW.L> rising 1.2 percent to 1.9 percent.
The sector was hit after UK finance minister Philip Hammond said in his Budget on Wednesday that the government would reclaim land that was not developed quickly enough.
"We're keeping our eye on the housebuilders," John Moore, trader at Berkeley Capital, said.
"We had quite a bearish budget for the housebuilders and we think they're just generally overpriced as it is," Moore added.
Among mid caps, pub operator Mitchells & Butlers <MAB.L> tanked 7.6 percent after reporting its full year earnings.
The company's full year profit slid due to higher costs, and said that it would not pay an interim dividend in 2018.
(Reporting by Kit Rees; editing by Ralph Boulton)