Prime Minister Theresa May's Conservatives have indicated that they will include a cap on energy prices for domestic customers in their election manifesto and Fallon said they were committed to making the markets work better.

"There's not been enough ability for people to switch, we haven't seen the competition we were hoping to emerge amongst the energy companies," Fallon told BBC radio.

"Therefore it's right to look at the way they are regulated and it's right where we can to protect people against large and arbitrary increases in their bills."

(Reporting by Michael Holden; editing by Kate Holton)

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