Oil traders should face prison if found guilty of conspiring to fix prices, prime minister David Cameron has warned.

He said the allegations were “hugely concerning” and that anyone held responsible would face major consequences if the claims were proved true.

“It’s totally unacceptable for firms to fix prices and force consumers to pay more. That’s why we’re looking at how to extend this criminal offence to the energy sector to make sure those who manipulate benchmark prices feel the full force of the law.”

Meanwhile Ed Davey, Secretary of State for energy, said in a statement to Parliament, that companies found guilty of price-fixing would feel the full force of the law, and could face heavy fines.