LONDON (AFP) - Britain's splintered government was rocked on Friday (April 26) by a growing scandal over who leaked news that Prime Minister Theresa May has conditionally allowed Chinese giant Huawei to develop the UK 5G network.

The highly controversial decision was reportedly made at a meeting on Tuesday (April 23) of Britain's National Security Council despite opposition from some ministers who are seen as potential candidates to replace Mrs May.

National Security Council discussions are only attended by senior ministers and security officials who first sign the Official Secrets Act that commits them to keep all conversations private or risk prosecution.

But The Telegraph newspaper broke the news late on Tuesday that Mrs May approved granting Huawei permission to build up "non-core" elements of Britain's next-generation telecommunications network.

The United States is adamantly opposed to Huawei's involvement because of the firm's obligation under Chinese law to help its home government if asked, including in intelligence matters.

British media reported that Cabinet Secretary Mark Sedwill - the country's most senior civil servant - gave those present an ultimatum until Thursday afternoon to deny responsibility for the leak.

Foreign Secretary Jeremy Hunt and Defence Secretary Gavin Williamson did so first.

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Mr Hunt called it "utterly appalling" and Mr Williams described it as "completely unacceptable".

They were soon joined by interior minister Sajid Javid - who like Mr Hunt is one of the front runners to succeed Mrs May as Conservative Party leader - and at least one other attending Cabinet member.

Mrs May herself said on Thursday that she does not comment on National Security Council meetings.

Sky News reported on Friday that the ongoing government inquiry into the source of the leak could become a formal criminal investigation.

Former Cabinet secretary Gus O'Donnell told BBC radio that the disclosure of National Security Council information was "incredibly serious" and a "complete outrage".

"This is really important for the country, these issues are massively important," he said.

Mrs May's government has been experiencing strains for months.

Disputes over Britain's stalled withdrawal from the European Union have seen several ministers resign.

Mrs May herself has promised to step down as soon as she gets the first stage of Brexit over the line. The new extended deadline for the process is now Oct 31.

Her commitment to quit has only fomented Cabinet rivalries as various ministers jockey for position in a looming leadership race.

Mrs May's spokesman said on Wednesday that a formal decision on Huawei would be made by June.