Senior MP Keith Vaz is to write to the Metropolitan Police to seek clarification on why the partner of Guardian journalist Glenn Greenwald David Miranda was held and questioned by officers while travelling through Heathrow.
Speaking on BBC Radio 4's Today programme, Mr Vaz said:"What needs to happen pretty rapidly is we need to establish the full facts.
"Now you have a complaint from Mr Greenwald and the Brazilian government - they indeed have said they are concerned at the use of terrorism legislation for something that does not appear to relate to terrorism - so it needs to be clarified, and clarified quickly.
"What is extraordinary is they knew he was the partner (of Mr Greenwald) and therefore it is clear people who are directly involved are being sought but also the partners of those involved".
The partner of Guardian journalist Glenn Greenwald who wrote a series of stories revealing mass surveillance programmes by the US National Security Agency (NSA) was detained for nine hours at London's Heathrow Airport under the Terrorism Act and his possessions confiscated.
David Miranda was passing through the airport on Sunday on his way home to Rio de Janeiro. Mr Miranda was questioned under schedule 7 of the Terrorism Act 2000 which applies only at airports, ports and border areas, allowing officers to stop, search and detain individuals, the Guardian reported.
A Metropolitan Police spokesman said: "At 08:05 on Sunday 18 August 2013 a 28-year-old man was detained at Heathrow Airport under Schedule 7 of the Terrorism Act 2000.
"He was not arrested. He was subsequently released at 17:00."