Ed Davey says he "can't even remember" an alleged agent giving him a £5,000 donation in 2013

Sir Ed Davey was energy secretary at the time and had just visited China but says "there's completely no link whatsoever".

It comes as MI5 issued a rare warning that an alleged Chinese agent infiltrated Parliament to interfere with UK politics.

An alert from the security service claimed Christine Ching Kui Lee "established links" for the Chinese Communist Party (CCP) with current and aspiring MPs.

She then gave donations to politicians, with funding allegedly coming from foreign nationals in China and Hong Kong.

Parliamentary records show Sir Ed received a £5,000 donation from Christine Lee in 2013 when he was energy secretary in the coalition government.

Sir Ed, Liberal Democrat leader and MP for Kingston and Surbiton, told Sky News today (January 14): "I was shocked by these revelations. The donation was taken and registered in the normal way, the correct way.

"The real question is, how are [security services] going to help politicians, political parties, Whitehall and all of us guard against state actors from other countries, particularly China."

He added: "I can't even remember this woman to be frank".

"The real issue is how the Chinese government, through different agents, are trying to infiltrate our democracy. Our secret services need to make sure that we are fully protected."

The allegations against Ms Lee emerged after a "significant, long-running" investigation by MI5, Whitehall sources told the BBC.

Home Secretary Priti Patel said it was "deeply concerning" that someone "who has knowingly engaged in political interference activities on behalf of the Chinese Communist Party has targeted parliamentarians".

But she said the UK has measures in place "to identify foreign interference". Christine Lee & Co Solicitors has been contacted for comment.

A spokesperson for the Liberal Democrats told the Local Democracy Reporting Service: “Ed is shocked by these revelations and the email from the Speaker of the House of Commons today was the first time he has been given cause to be concerned about a donation to his local party association received in 2013.

“The Government must make it a national security priority to protect the UK's democracy from threats and interference by foreign actors.

“This donation was reported properly and all rules and guidance was followed - as Ed expects is the case with donations made to colleagues across the House.”