A secretive US spy court has renewed the National Security Agency's authority to continue its controversial surveillance programmes, involving tapping of phone calls of people across the globe.

On 3 January, the US Foreign Intelligence Surveillance (FISA) court renewed the NSA phone collection programme, following a periodic request by the US government, according to Shawn Turner, a spokesman for the Office of the Director of National Intelligence.

Such periodic requests have been in place since the programme started in 2006. This was the 36th time the court approved the NSA's bulk collection of telephone metadata.

Turner noted that the Office of the of National Intelligence decided to declassify the FISA Court ruling in the light of the significant and continuing public interest in the phone metadata collection programme.

The office, however, said it is open to modify its programmes in line with the suggestions of a presidential review panel.

"The intelligence community continues to be open to modifications to this programme that would provide additional privacy and civil liberty protections while still maintaining its operational benefits," Turner said.

Administration's Continued Defence

The Obama administration and the intelligence office have defended the NSA's controversial surveillance programmes, saying they are required to ensure national security.

The latest development comes as part of the administration's move to justify its spying actions that came to light following disclosures by former NSA contractor Edward Snowden.

The Obama administration is considering the recommendation of a presidential advisory group for "transitioning the programme to one in which the data is held by telecommunications companies or a third party".

The advisory group presented 46 recommendations to change the NSA programmes in December. The recommendations included banning the NSA from collecting and storing phone records without obtaining separate court approval for each search.

President Barack Obama noted that he will review the recommendations and make necessary reforms in the NSA surveillance programmes.

Separately, the government appealed a major ruling against the agency by District Judge Richard Leon last month, saying that the programme was "almost-Orwellian" and likely unconstitutional.

"I cannot imagine a more 'indiscriminate' and 'arbitrary invasion' than this systematic and high-tech collection and retention of personal data on virtually every single citizen for purposes of querying and analysing it without prior judicial approval," he wrote.

"Surely such a programme infringes on 'that degree of privacy' that the founders enshrined in the Fourth Amendment."