Britain's FTSE bounces back on ECB stimulus hopes, energy shares up

* FTSE 100 up 1.3 pct after falling in last 3 sessions

* Energy stocks gain, track crude oil prices

* Sainsbury's volatile after trading update

* Boohoo.com plunges following profit warning

By Atul Prakash

LONDON, Jan 7 (Reuters) - Britain's top equity index rebounded from a three-week low on Wednesday as euro zone consumer price data raised expectations of new stimulus from the European Central Bank and energy shares tracked oil prices higher.

The blue-chip FTSE 100 index, which had fallen in the last three sessions and hit its lowest since mid-December on Tuesday, was up 1.3 percent at 6,446.07 points by 1525 GMT.

Data showing euro zone consumer prices fell more than predicted in December heightened expectations the ECB will announce a government bond-buying programme at its policy meeting later this month to try and revive prices and the euro zone economy, analysts said.

"The ECB is definitely planning to go for a much wider quantitative easing programme, although the political uncertainty in Greece is going to make things a little difficult for (ECB President) Mario Draghi," said John Smith, senior fund manager at Brown Shipley.

Among sectoral gainers, energy stocks topped the list. The UK Oil and Gas index rose 1.1 percent after recent sharp declines, mirroring some gains in battered crude oil prices.

Retail stocks remained choppy. Sainsbury's rose more than 4 percent in early trading after reporting better-than-expected results in the Christmas quarter. But its shares were last down 2.1 percent on concern it might lose more market share to discounters and could suffer in an intensifying price war.

"Sainsbury's numbers were better than expected, but I am not a buyer of the stock for now, as top line guidance remains unchanged," said Securequity sales trader Jawaid Afsar.

Grocer Tesco, which posts an update on Thursday, was up 2.3 percent and Marks & Spencer (Other OTC: MAKSF - news) rose 3.6 percent. WM Morrison shares, however, were down 1.3 percent.

European stock markets have been choppy in the past days ahead of a Jan. 25 election in Greece. Investors are concerned that if the Syriza party leads the next government, then the risk of a sovereign default for Greece will increase and the country could leave the euro zone. Syriza has promised to end austerity and renegotiate the country's debt.

Among other retailers, shares in the online fashion company Boohoo.com, which is not in the FTSE 100 index, slumped by around 40 percent after cutting its profit outlook.

Aggreko (LSE: AGK.L - news) , which fell 12 percent in 2014, was up 2.6 percent. The world's biggest temporary power provider raised its 2014 trading profit expectations following a debt settlement. (Additional reporting by Sudip Kar-Gupta; Editing by Larry King and Susan Fenton)