WASHINGTON: A US federal judge in New York ruled on Friday that the massive collection of domestic telephone data by the US National Security Agency is lawful, rejecting the American Civil Liberties Union’s plea to declare it illegal.

A former NSA employee, Edward Snowden, blew the whistle on the programme when he leaked hundreds of documents earlier this year, showing how the agency was monitoring millions of telephone subscribers both at home and abroad.

“We are pleased the court found the NSA’s bulk telephony metadata collection programme to be lawful,” said Justice Department spokesman Peter Carr while commenting on the judgment.

The decision conflicts with that of a US District Court judge who ruled against the government early last week, declaring the programme unconstitutional.

An ACLU representative said they would now take their case to a superior court. “We are extremely disappointed with this decision, which misinterprets the relevant statutes, understates the privacy implications of the government’s surveillance,” said Jameel Jaffer, ACLU’s deputy legal director.

“As another federal judge and the president’s own review group concluded last week, NSA’s bulk collection of telephony data constitutes a serious invasion of Americans’ privacy. We intend to appeal and look forward to making our case in the Second Circuit.”

In a 53-page opinion, US District Judge William Pauley said the legality of the programme was “ultimately a question of reasonableness”, under the Fourth Amendment and represents the US government’s “counter-punch” to eliminate the Al Qaeda terrorist network.

Judge Pauley said that if the US government had the phone data collection programme before the Sept 11, 2001, terrorist attacks, it could have helped provide critical clues.

“The government learned from its mistake and adapted to confront a new enemy: a terror network capable of orchestrating attacks across the world,” the judge said.