David Davis - a one-time Tory leadership contender - said that ministers including "almost certainly the Prime Minister" would have known police planned to hold David Miranda at Heathrow.
While they did not direct the nine-hour detention they approved it by implication, Mr Davis said.
The decision to hold Mr Miranda under terrorism laws has provoked fierce debate about civil liberties.
Mr Davis's comments came as the Conservative Home Secretary Theresa May admitted she had known in advance that Mr Miranda was to be detained.
Mrs May said it was right for police to act if they thought a person was in possession of highly sensitive stolen information that could help terrorists.
The White House admitted it had been given a "heads up by the British Government" that the detention was likely to happen.
Downing Street yesterday confirmed David Cameron had been "kept abreast" of developments.
The UK's independent reviewer of terrorism legislation, David Anderson, QC, who has already described the length of Mr Miranda's detention as "unusual", is to lead a review into the case.
Lawyers for Mr Miranda, the partner of Guardian journalist Glenn Greenwald, who has led much of the reporting on Mr Snowden, are planning to challenge the legality of his detention under the Terrorism Act.