On Thursday Britain's domestic counter-intelligence service, MI5, issued an "interference alert" about a "potential threat" posed by Christine Ching Kui Lee, a lawyer with offices in China and the UK.

The alert said Lee "acted covertly" with the United Front Work Department of the Chinese Communist Party to interfere in UK politics by cultivating links with parliamentarians "across the political spectrum" and facilitating donations "on behalf of foreign nationals," MI5 said.

Lee's firm was advertised on a website of the Department of International Trade (DIT) as recently as Friday, before being taken offline.

In a statement a DIT spokesperson told CNN: "The department has no record of any relationship with Christine Lee."

CNN has contacted Lee for comment but has not received a reply. On Friday, China's Foreign Ministry denied that Lee was a Chinese "agent" and said Beijing "has no need and will not engage in so-called interference activities."

"We urge relevant British officials to refrain from making groundless remarks or hyping up the 'China threat' theory for ulterior political purposes," Chinese Foreign Ministry spokesperson Wang Wenbin said.

A CNN analysis of Britain's parliamentary register, by which lawmakers record donations, shows Lee gave at least £461,000 ($639,000) to Barry Gardiner, an elected member of the opposition Labour party between 2014 and 2020, mostly through funding of his staff. Her son even worked in his office and had a parliamentary pass.

Lee also donated £5,000 ($6,800) to the leader of the Liberal Democrat party Sir Ed Davey in 2013.

It is not illegal for Lee to make the donations as the UK does not yet have a foreign agents registration act like the United States, nor is it illegal for a British citizen or foreign national working in the UK to be affiliated with the Chinese Communist Party. Lee is listed as a British national in the UK's corporate registry.

In a statement to CNN, Gardiner said he had not benefited personally from Lee's donations in any way. The money had been properly reported and its source verified.

"I will continue to work closely with our security services in this and all other matters that relate to the security of our country," Gardiner said.

Davey told CNN his local association had accepted the donation, that it was reported properly, and that "this was the first time he had been given cause to be concerned."

"The government must make it a national security priority to protect the UK's democracy from threats and interference by foreign actors," Davey said.

Lee's services advertised on UK government portal

The London offices of Christine Lee and Co.

The payments were made through Lee's eponymous law firm Christine Lee & Co Solicitors, which since at least 2016 has been included in the directory of the "UK Advisory Network" -- a list of business services compiled by what is now the Department for International Trade to, as the directory says, "provide an accessible route" "to foreign investors setting up in the UK."

A preface to the directory says it is "facilitated by invitation from the UK government" and that "members go through a robust vetting procedure to join."

"The Network provides a forum for feedback to the government on issues affecting the business environment and ultimately informs efforts to make the UK even more business friendly," it says.

Lee's services could still be accessed through the Department of International Trade on Friday via a government portal recently revamped to attract overseas investment for UK projects.

The advertisement for Lee's firm on the UK's great.gov website offered the first hour of legal advice for free, as did the other firms listed.

A disclaimer on the site said the department does not "endorse the character, goods, services or ability of the members of the directory" and that there is no legal relationship between the department and the service providers listed.

The Department of International Trade said in response to CNN it had to do a "fair amount of digging" on the matter and that the great.gov.uk page was no longer live, although the site was up on the web until the close of business on Friday.

"This case shows is an abject failure of government vetting, and shows extraordinary naivety on the part of the government when it comes to the purpose of these kinds of institutions and individuals," said Luke de Pulford of the Inter-Parliamentary Alliance on China, which is pushing for tougher rules on China.

To have somebody who MI5 published an alert about "advertising their services on the government website truly is remarkable and needs to be dealt with as soon as it possibly can be," he said.

Photographed with prime ministers

Lee, a former legal adviser to China's embassy in London, has been active in political circles for 15 years.

She first set up the British Chinese project in 2006 to encourage British citizens with Chinese ancestry to vote in the UK. From 2011 onwards she was involved in a now-defunct All Party Parliamentary Group called Chinese in Britain.

She has been photographed with former Conservative Prime Ministers David Cameron and Theresa May. The latter even gave her an award two years ago for her work with Britain's Chinese community.

According to the UK's Companies House register, Lee has a web of property, legal, cultural and educational ventures under her name.

A copy of a letter sent by the Lords Speaker in the House of Lords, the UK's upper chamber, and obtained by CNN said Lee has facilitated donations "on behalf of foreign nationals based in Hong Kong and China. This facilitation was done to covertly mask the origins of the payments."

"This is clearly unacceptable and steps are being taken to ensure it ceases." the letter reads.

The Home Office launched a consultation last year on new legislation designed to shore up safeguards against hostile state action. Parliamentary sources told CNN the bill is expected be presented to the House of Commons during the early part of this year.

When CNN visited the London office of Lee's law firm, in the heart of Soho, it appeared to have been shuttered for some time with the windows thick with dust. It was empty with a notice in the window saying it had closed because of the pandemic. Emails and calls to the contact details provided in the sign went unanswered.

In a piece written for the UK's Daily Mail in 2020, the firm said: "Christine Lee & Co is proud of its record of public service and the support it has provided to the democratic process. We have never sought to influence any politician improperly or to seek any favours in return for the support that we have provided."

Ian Duncan Smith, the former leader of the ruling Conservative party and a fervent critic of China, raised the alarm about Lee in Parliament on Thursday, saying MI5 had warned the House Speaker Lindsay Hoyle that "an agent of the Chinese government" had been actively working to "subvert" the process of parliament.

"This is a matter of grave concern," he said.