Theresa May: 'I was briefed in advance'
20 August 2013 Last updated at 17:52 BST
The Prime Minister's office was "kept abreast" of the decision to detain David Miranda, the partner of Guardian journalist Glenn Greenwald.
Mr Miranda was held at Heathrow airport for nine hours on Sunday while in transit from Germany to Brazil.
Home Secretary Theresa May said she was briefed in advance that there was a a possibility of stop and search and that it was right for the police to act.