By Kit Rees
LONDON (Reuters) - A fall in Centrica's (L:CNA) shares weighed on British stocks on Thursday, but a rebound in housebuilders and a weak pound provided enough support to recoup most of the morning's losses.
Britain's blue chip FTSE 100 (FTSE) index closed down 0.02 percent at 7417.24 points.
Centrica (L:CNA) was by far the biggest faller, down 15.5 percent - its biggest one-day loss since listing in 1997, after the utility gave a disappointing trading update.
Centrica said 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 (L:NG) and SSE (L:SSE) also declined 2.8 percent and 0.6 percent respectively.
Babcock (L:BAB) was the second-weakest performer of the FTSE, retreating in the wake of brokers cutting their target prices after the engineering outsourcing group published its results on Tuesday.
Housebuilders recouped some of the previous session's losses, with Berkeley Group (L:BKGH), Barratt Developments (L:BDEV) and Taylor Wimpey (L:TW) all rising close 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.
Sage Group (L:SGE) was the FTSE's biggest gainer, up 2.7 percent after several brokers upped their price targets for the stock.
British water utility Severn Trent Plc (L:SVT) rose 0.6 percent after it reported a 4.4 percent rise in half-year profit.
Among mid caps, pub operator Mitchells & Butlers (L:MAB) closed about 7 percent down 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.