Guardian newspaper editor Alan Rusbridger said the decision to detain David Miranda "seems to me a clear misuse of a law."
Speaking at the Edinburgh International Book Festival, he called for a wider public debate about mass surveillance, praised the value of the information leaked by whistleblower Edward Snowden and described US soldier Bradley Manning's 35-year sentence "staggering".
Mr Rusbridger said the "strong suspicion" has to be that the detention of Mr Miranda at Heathrow Airport was "quite a carefully planned operation and wasn't random".
"There has to be a debate. There hasn't been much of a debate in this country yet because everyone is a bit complacent about it," he said. "In the end it's for people to decide."
The independent reviewer of terrorism legislation said he will examine the detention of David Miranda at Heathrow Airport.
Nick Clegg has backed David Cameron's decision to send a top civil servant to The Guardian to urge them to destroy classified data.
The Guardian journalist whose partner was held at Heathrow Airport hits out at the UK as he gives ITV News his first British TV interview.