Conservative MP Andrea Leadsom has hit back at Alistair Darling and George Osborne's open letter to the Leave campaign, describing it as "extraordinary" and underlining her belief that staying in the European Union "won't help the UK".
The letter from the current and former chancellors, which was released on Wednesday evening, claimed that the Leave campaign's bid to exit the EU would bring with it a "massive unquantifiable risk" and place jobs and the economy at risk.
But the minister for energy and climate change told Julia Hartley-Brewer that staying in the European Union will not help the United Kingdom.
"That letter is rather extraordinary," she said. "Most of the world is not in the European Union. The European Union is the slowest growing economic bloc anywhere, other than Antarctica.
"Even the European Commission themselves agree that the single market for services doesn't work.
"Yet the EU's singular failure to achieve free trade agreements to our priority export countries means they're holding us back.
"Frankly [Darling and Osborne] need to answer the question: 'why do you have so little faith in the UK?'"
Leadsom added that a vote to leave would allow Britain to strike unique deals to safeguards its future.
"We will have a British option, it won't be Norwegian, it won't be Icelandic. It won't be any of those things," she said.
"What we will have is the £10 billion net a year that we're currently paying across to the EU that we get nothing for at all, that's just the price of membership.
"We'll be able to control our own borders, and trade freely with the European Union.
"It’s just a tactic to say [trading with the EU] all hinges on which option you choose. Countries trade with each other on the basis of business-to-business ties, historic links and so on."
Darling and Osborne's letter also alleged that entering into a free trade agreement with continental Europe after an EU exit would hinge on Britain maintaining free movement for citizens of EU countries.
But the MP for South Northamptonshire said: "It's simply not true to say that you can't have free trade without free movement.
"The issues for other EU members are very different from those for the UK. Those who are members of the euro, you cannot walk away from a shared currency."