The Government yesterday ruled out an early return to "normal" airport security despite an ultimatum from budget airline Ryanair.
The Irish no-frills carrier said it would sue the Government for compensation for delays unless usual security resumed within seven days.
But the Department for Transport said it had "no intention of compromising security".
Ryanair, whose chief executive Michael O'Leary described recent security measures as "farcical and Keystone Cops-like", said it was basing its compensation claim on the Transport Act 2000.
But the DfT said it directed aviation security measures under the Aviation Security Act 1982.
The DfT said: "The security regime in place at UK airports is necessary because of the level of security threat.
"We have no intention of compromising security levels nor do we anticipate changing requirements in the next seven days."
Mr O'Leary said recent measures had been "completely ineffectual and stupid" and added terrorists "must be rolling around the caves of Pakistan laughing".
He said the ban on such items as water bottles and toothpaste was "insane", adding "We are not in danger of dying at the hands of toiletries".
Mr O'Leary added: "The best way to defeat terrorists and extremists is for ordinary people to continue to live their lives as normal.
"Because of additional security restrictions imposed last Thursday, the shambles at the London airports has been anything but normal.
"The UK Government successfully led the return to normality of the London Underground within two days of the July 7 terrorist attacks.
"It is important they now restore security at the London airports to normality and remove these nonsensical, and (from a security perspective) totally ineffective restrictions."