If Britain opts out of European Union (EU), it would result in $700 million (GBP 500million) gas and power bills additionally per annum. Energy Secretary Amber Rudd has cautioned that Britain's energy security at risk if Brexit takes place. UK energy costs are projected to soar if Britain moves out of EU. 

Brexit may threaten Britain's energy security. Amber Rudd has cautioned the possible energy shock in terms of higher costs for Britain, if the UK comes out of EU. However, Rudd is optimistic of internal market that would assure energy security to some extent. 

Bloomberg reports that Amber Rudd's remarks are in line with Prime Minister David Cameron's optimism. Cameron says Britain government and economy are "stronger, safer and better off" among the 28 members of European Union. Britain's voters gear up for a referendum on Brexit on 23 June 2016. Prime Minister Cameron and his associates are optimistic of Britian's economy strength. 

Amber Rudd said in a speech in Southeast England that "if we left the European internal market, we'd get a massive electric shock because UK energy costs could rocket. However you look at it, an internal energy market helps to guarantee our energy security, which is the bedrock of our economic security. I'm not willing to play fast and loose with either."

The Guardian further adds that Brexit would result in jacking up airfares for UK holidaymakers and business travelers. If Britain votes to leave EU, there would be fewer scheduled flights between the UK and European Union. Business travelers will have to face higher air fare. European Health Insurance Card and financial protection for holiday packages will also be at risk. Brexit will affect consumer protection as well, according to Association of British Travel Agents (Abta).  

Rudd further said: "We mustn't let our energy security be hijacked as a political pawn to bring Europe to its knees. By working together in the European Union we can stop this becoming a reality. By working together 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."

Meanwhile, US investment giant Black Rock has also cautioned Cameron's government that leaving the EU would impact Britain economy in more negative way. After the referendum also, Cameron's government will have to face tremendous pressure to get controversial legislation through the Commons. There may be division of opinion within the party as well, it further cautioned, as reported by The Telegraph.

Britain has more bargaining power by working within 28-nation bloc EU. Britain has bargaining power to diversify sources of gas and push down prices. She also highlighted the specter of Russian President Vladimir Putin utilizing gas supplies as "a tool of foreign policy." Rudd was speaking at the BritNed interconnector near Rochester in Kent, a county that's shown significant support for the anti-EU.