The U.S. government warned Britain that it would be “madness” to use Huawei technology on the U.K.’s 5G network.

A delegation from Washington presented a document yesterday in London with evidence that demonstrated the security risks posed by the use of the Chinese telecommunications company in the network that the European country intends to install.

Senior U.S. officials, led by Deputy National Security Adviser Matt Pottinger, handed over a dossier that, according to sources, questioned British intelligence’s own technical assessment that it would be possible to use Huawei on the 5G infrastructure without risk to national security, a BBC report revealed.

Members of the delegation warned that allowing the Chinese firm access would be “nothing short of madness,” The Guardian reported.

The British media recalled that the president of the United States himself, Donald Trump, had personally discussed the issue with Prime Minister Boris Johnson months ago.

This new presentation is considered the last warning issued by the Trump administration to the British government to reconsider its decision to allow the controversial Chinese company to supply some “non-core” parts for the UK’s 5G network.

Last year, the United States banned companies from selling components and technology to Huawei and 68 related companies.

“It is a national security threat,” Trump said in August after Washington blacklisted Huawei. “It’s a company we may not do business with at all,” he said.

That is why Washington had previously warned that any use of the Chinese company would lead to a review of the intelligence exchange with London.

However, MI5 chief Andrew Parker told the Financial Times that he has “no reason to think” that the UK’s intelligence-sharing relationship with the United States would be adversely affected if Britain used Huawei technology.

Conservative MEP Bob Seely said that Huawei “is to all intents and purposes part of the Chinese state” and an agreement with the technology giant would in effect allow Beijing access to the UK’s network.

That is why Seely asked Parliament’s Foreign Affairs Committee to open an investigation into the company’s suitability to build parts of the UK’s 5G infrastructure.

In a column published on the Conservative Home website, the congressman noted that the Chinese regime “is a cyber risk,” noting that it has “a dreadful reputation for cyberattacks and intellectual property theft against Western and global institutions and firms.”

In that sense, he recalled that Huawei has been the object of an investigation in the United States for fraud and commercial espionage, and that the United States together with Australia banned Chinese high technology in their 5G networks.

“We need to do the same to support our Western alliances and to protect our security, our people, and our values,” he said.

A government spokesman, quoted by Reuters, had said days earlier, “The government continues to consider its position on high-risk vendors and a decision will be made in due course.”