Andrea Leadsom, who has likened herself to Margaret Thatcher in her bid to be the next Conservative leader, said that leaving the European Union would be a "disaster" – despite being one of the leading voices in the Brexit campaign.

The junior energy minister, who is also emerging a serious contender in the Conservative leadership contest, said in a recording three years ago at the Hansard Society’s annual parliamentary affairs lecture that she was going “to nail my colours to the mast here”.

In the recording, obtained by the Mail on Sunday, Ms Leadsom added: “I don’t think the UK should leave the EU. I think it would be a disaster for our economy and it would lead to a decade of economic and political uncertainty at a time when the tectonic plates of global success are moving.

“Like the rise and fall of the Roman and Greek Empires we are seeing the rise of the Asian and South American economies at a time when our own future is less certain. And to be honest economic success is the vital underpinning of every happen nation. The wellbeing we all crave goes hand in hand with economic success.”

A spokesperson for Ms Leadsom told the Independent that the recording was “taken completely out of context.” It is “complete nonsense,” they added.

Mrs Leadsom defended her statement on the Andrew Marr Show: "It has been a journey.

"When I came into Parliament, like most people in the country I'd grown up as part of the EU and it's absolutely part of our DNA and I came into Parliament, set up something called the Fresh Start Project, which took hundreds and hundreds of hours of evidence about how the EU impacts on the UK - on everything from immigration to fisheries and so on.

"During that process I travelled all across Europe with lots of parliamentary colleagues - up to 100 Conservative colleagues supporting this work - to try and get a really decent, fundamental reform of the EU."

Tory leadership race underway

According to the newspaper she opened the lecture by saying that the EU, however, needed major reforms in order for it to be “sustainable”. Ms Leadsom added that the democratic consent for the EU in Britain was “wafer thin”.

Meanwhile, Ms Leadsom, a former City worker, likened herself to Margaret Thatcher and praised the late Prime Minister’s ability to mix toughness with “personal warmth” in an interview with the Sunday Telegraph. “As a person, she was always kind and courteous and as a leader she was steely and determined,” she said.

“I think that's an ideal combination - and I do like to think that's where I am.”

The favourites in the Tory leadership race Show all 5 1 /5 The favourites in the Tory leadership race The favourites in the Tory leadership race Theresa May The longest-serving Home Secretary in 100 years took a back seat in the referendum campaign. While backing Remain, she did not hit the campaign trail and delivered only a handful of speeches and interviews, and was critical of many aspects of the EU, particularly the European Convention on Human Rights. Hedging her bets allows her to now emerge as a ‘unity’ candidate, and she is said to have been building up her back-room staff in preparation for a leadership bid. She has the significant advantage of having served in one of the great offices of state, in a steady and competent manner that has won her many admirers within party and the civil service. At a time of great instability, it may be that she is viewed as steady hand on the tiller. Mrs May does however, lack the ‘star quality’ of a Boris Johnson and party members may doubt her ability to connect with ordinary voters PA The favourites in the Tory leadership race Michael Gove The Justice Secretary may be able to set himself up as ‘the thinking Tory’s Brexit candidate’. Made an enormous political and personal decision to back Leave, taking on his old friend David Cameron. He performed well during the TV debates, and will be an admired figure among Eurosceptic Conservatives. Along with Johnson, he will be hindered by the fact that he led a very divisive campaign, characterised by ‘blue-on-blue’ action. MPs may also judge that he lacks Boris Johnson’s wider appeal with the electorate. Possibly more likely that he will settle for being his new bosom buddy Boris’s Chancellor Getty The favourites in the Tory leadership race Stephen Crabb Highly-rated Work and Pensions Secretary, raised on a council estate, so could reach out to non-traditional working class Tory voters Getty Images The favourites in the Tory leadership race Andrea Leadsom Minister of State for Energy at the Department of Energy and Climate Change is one of the most prominent figures in the Leave campaign, seen to have performed well in TV debates Rex Features The favourites in the Tory leadership race Liam Fox British Conservative MP and former Secretary of State for Defence, as sources said he will stand for the leadership of the Conservative Party AFP/Getty

It comes as the most recent polling of the Conservative leadership contest places Theresa May, the Home Secretary, as racing towards victory in her bid to succeed David Cameron. Ms May was backed by 60 per cent of Tory voters, with Mr Gove second on 10 points and Ms Leadsom on six, according to the ICM poll for the Sun on Sunday.

Among party members, who will vote to decide the winner of the leadership contest, some 46 per cent say she would make the best Prime Minister. She has also been backed by more MPs, who select the final two candidates to go on to the ballot paper.