Soaring energy costs have become a big political issue in Britain, leading to intense scrutiny of utility companies like Centrica, after Ed Miliband, the leader of Britain's main opposition party, promised to temporarily freeze bills if he wins power.

Centrica said on Tuesday the search for a new finance chief was underway, adding that Luff would leave some time before December 31, 2014, but the date was yet to be confirmed.

At Reed, Luff, who prior to Centrica worked at shipping group P&O, will be chief financial officer, replacing Duncan Palmer, who said he would leave the Anglo-Dutch media group due to family circumstances this September.

Luff, Centrica's group finance director since 2007, is part of a team credited with improving the British Gas-owner's cost base and competitiveness and expanding into the U.S. market.

Shares in Centrica, which have dropped 14 percent since September when Miliband announced his plan to freeze bills, were down 0.8 percent at 339.70 pence in morning trading, underperforming the benchmark FTSE-100 index.

"Nick Luff is widely regarded as one of the best CFOs in the European utility sector. We see Luff's departure as a slight negative for Centrica," Royal Bank of Canada analyst John Musk said.

Sam Laidlaw, Centrica's chief executive since 2006, said Luff had made a "significant and lasting contribution" to the company.

Luff's departure from Centrica follows that of the chairman Roger Carr. He stepped down at the end of last year and was replaced by the former head of Network Rail, Rick Haythornthwaite.

(Reporting by Kate Holton and Sarah Young; Editing by Mark Potter)

Stocks treated in this article : REED ELSEVIER, Centrica PLC, Reed Elsevier plc