David Cameron said Argentinian President Cristina Kirchner should respect the outcome of the referendum on the Falkland Islands set to be held later this year.
The Prime Minister said if Falkland Islanders wanted to remain part of Britain, they would have his "100 per cent backing".
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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.