A FULL investigation will be held into the UK's energy market in a bid to "rebuild" consumer trust, it has been announced.
Regulator Ofgem says the Competition and Markets Authority (CMA) probe should ensure "once and for all" that competition works effectively.
The investigation, expected to take about 18 months, will look at the relationship between the supply businesses and generation arms of the Big Six energy firms.
It will also study the Big Six's profits, as well as any barriers to entering the market.
Ofgem chief executive Dermot Nolan said: "Now is the right time to refer the energy market to the CMA for the benefit of consumers.
"There is near-unanimous support for a referral and the CMA investigation offers an important opportunity to clear the air.
"This will help rebuild consumer trust and confidence in the energy market as well as provide the certainty investors have called for.
"The energy market is also going to change rapidly over the next few years with the roll-out of smart meters, the Government's electricity market reforms, and closer integration with European energy markets.
"A CMA investigation should ensure there are no barriers to stop effective competition bearing down on prices and delivering the benefits of these changes to consumers."