Brexit would cause a £500 million 'electric shock' to the UK's economy

Power bills would rise more than £500 million ($704 million) if Britain left the EU on 23 June, according to the UK's energy secretary.

Amber Rudd is expected to warn on Friday that "Brexit" - Britain voting to leave the European Union - would result in a "massive electric shock" to the UK thanks to "skyrocketing" energy costs, according to the Guardian.

If true, the claim means that energy bills would rise more than £20 per household in the UK.

The claim is based on a report from National Grid consultants Vivid Economics. The National Grid itself has no political view on Brexit, but Vivid Economics' report says "the impact of Brexit on the UK energy system is very likely to be negative."

Rudd is expected to say that energy is a political concern, during a visit to an interconnector pipeline in Kent.

"We can't let our energy security be hijacked as a political pawn to bring Europe to its knees. By working together in the European Union each member state can stop this becoming a reality."

She will reportedly add that the EU is stronger together, and that EU states have a common concern that requires unity:

"As a bloc of 500 million people, we have the power to force Putin's hand. We can coordinate our response to a crisis. We can use the power of the internal market to source gas from elsewhere. We can drive down the price of imports, as has happened recently in eastern Europe.

"To put it plainly - when it comes to Russian gas, united we stand, divided we fall."

But not everyone is convinced. Matthew Elliot, Vote Leave's campaign chief, called the claims "absurd," according to the Financial Times.

"It is quite extraordinary the extent to which the government is willing to do down Britain in its desperate attempt to win the referendum," he said, adding that the EU actually made British energy bills more expensive.