A spokesman for the Prime Minister has said that he "does not resile" from a commitment he made in 2010 to above-inflation rises in the defence budget after 2015.
Downing Street insisted today that he had always been referring to 2016 onwards.
David Cameron told the House of Commons, when the Strategic Defence Spending Review was published and laid out plans for the military up until 2020, that his "strong view" was that the defence budget "will require year on year real terms growth in the years beyond 2015."
There is pressure within the Coalition Government to make further budget cuts across departments, as negotiations begin over the 2015-16 spending review.
Today, the Defence Secretary announced £159bn in military equipment spending - which makes up about half of the defence budget - until 2022.
More top news
Accompanied by the Duke of Edinburgh, the Queen will attend the opening ceremony of the fifth session in the Holyrood chamber.
Ms Leadsom has received the backing of Ian Duncan Smith, the former work and pensions secretary.
The former shadow work and pensions secretary is considered a more viable candidate than Angela Eagle, a Labour source has told ITV News.