* "Big Six" to publish long-term prices from March 31
* Not specified which exchange prices to be published on
* Utilities face financial penalties if they do not comply
By Nina Chestney
LONDON, Feb 26 (Reuters) - Britain's main energy suppliers will have to disclose long-term power prices twice daily from next month under rules to be enforced by regulator Ofgem aimed at encouraging new entrants into a fairer energy market.
From March 31, Britain's largest six energy suppliers -Centrica-owned British Gas, SSE, EDF Energy , RWE npower, E.ON and Scottish Power - will have to publish wholesale power prices for as far as as two years ahead at 1030 GMT and 1530 GMT on an exchange or face penalties.
Energy Secretary Ed Davey said on Wednesday that making prices more transparent will help reveal how the "Big Six" companies trade and make it easier for competitors to challenge their business model.
"Almost two million customers are with independent suppliers and we expect these reforms to help these suppliers and any new entrants to grow," Andrew Wright, Ofgem's chief executive, said in a statement.
Britain's utilites trade energy in the wholesale market via brokers and exchanges. Due to a low amount of market participants, there has been concern about a lack of liquidity for forward contracts.
Ofgem has not specified which exchange the companies had to use, a spokesman told Reuters.
Exchanges which currently offer UK wholesale power contracts include Intercontinental Exchange Group's ICE, Anglo-Dutch energy exchange APX and N2EX, operated by NASDAQ OMX Commodities and Nord Pool Spot.
The issue of rising energy bills has dominated the British political agenda since opposition Labour leader Ed Miliband promised to freeze energy bills for 20 months if he wins power in a 2015 election.
Political parties are competing with one another to be seen to be tough on what they say are unfair price rises.
Earlier this month, Davey said former gas monopoly British Gas might be broken up to put a stop to excessive profit margins, responding to a review by regulators.
Ofgem, the Office for Fair Trading and the Competition and Markets Authority have been carrying out an investigation into competition in Britain's energy retail market, looking at prices, profits and barriers to entry.
"Ofgem continues to think there is an issue around liquidity and transparency in the wholesale energy market," said Peter Atherton, utilities analyst at Liberum Capital.
"But whether (these rules) solve any of the problems is questionable."
SSE's chief executive Alistair Phillips-Davies also said that although the firm welcomed Ofgem's new rules, "all measures should apply to every player in the market to ensure there is a more liquid and transparent market for all".