A secret court that oversees the US government's legal surveillance requests rejected a record number of applications last year, according to new figures.

Newly released data by the US Courts show that the Washington DC.-based Foreign Intelligence Surveillance Court (FISA court) rejected nine applications during the final year of the Obama administration's tenure.

It's the largest number of requests the FISA court has denied in its entire four-decade history.

By comparison, the court announced at its last year's count that it didn't reject any government surveillance requests, which historically is not irregular.

The report shows that 1,752 applications were made during 2016 to allow the National Security Agency (NSA) and the Federal Bureau of Investigation (FBI) to intercept phone calls and emails. Breaking down that overall figure, the court said it permitted 1,378 requests in full, while 339 requests were granted after modification.

The court's new reporting methods also revealed that the FISA court also rejected parts of 26 requests submitted by the NSA and the FBI.

In other words, just 0.5 percent of all surveillance requests last year were denied.

By comparison, since 1979 to date, the court has approved 40,117 warrants but only rejected 21 requests. That's a rejection rate of 0.052 percent.

The figures are reported annually by the Justice Department to members of Congress, which also received a classified version of the report, as part of a requirement set out by the Freedom Act, passed in 2015 as an intelligence community reform effort after the Snowden revelations.

But the work of the court remains shrouded in secrecy. Founded in 1978, FISA court was tasked with processing government requests for surveillance against foreign targets. It was this court that approved a number of controversial programs, such as PRISM and the phone records collection program, which were later leaked by whistleblower Edward Snowden to journalists.

ZDNet has previously reported that the US government used the secret court in order to obtain source code from Silicon Valley tech companies.

Some of the provisions of the law that authorized the NSA's programs are set to expire at the end of this year. While the new Trump administration has said it wants Congress to reauthorize the law to keep its intelligence gathering programs in place, the government has refused to comply with congressmembers' demands to release figures on how many Americans are caught up in its surveillance programs.

Last week, it was confirmed that the FBI obtained a FISA warrant last year to monitor a Trump adviser, Carter Page, who authorities believe was acting as an agent on behalf of Russia.

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