An investigation into how CCTV footage of Matt Hancock kissing his female adviser was leaked to a UK tabloid newspaper has drawn attention to the privacy of politicians and officials working at the heart of the UK government.

The inquiry was launched last week by the Department of Health and Social Care to examine the chain of events that led to the former health secretary being filmed in his ministerial office apparently without his knowledge.

Hancock was forced to resign after footage of him kissing and holding aide Gina Coladangelo was leaked to The Sun newspaper.

According to senior government figures, one of the lines of inquiry being pursued by the health department investigation is whether staff at Emcor, the facilities management company which provides security for the ministry, were in some way involved in leaking the CCTV images.

The government figures believe the grainy footage was bought by TheSun newspaper for a large sum of money and that the video images mightoriginally have been sourced from an employee of Emcor.

The newspaper said the person who took the footage wanted to expose the hypocrisy of Hancock, a key proponent of Britain’s three lockdowns, who was breaking his own Covid-19 rules by kissing Coladangelo in his health department office.

Whitehall officials also said the inquiry had largely discounted the theory that Hancock could have been bugged by a hostile power.

Rather than being placed in the room to catch the health secretary, the camera was already there — in the same place on the ceiling — in 2017 when the department of health moved into the building.

The building was previously occupied by another government agency called the Parliamentary Estates Directorate.

At the time of the PED’s 2015 move into the Westminster building it took advice from the Metropolitan Police, parliament’s security team and a wing of the UK’s domestic security service MI5 called the Centre for the Protection of National Infrastructure.

Those groups recommended the installation of CCTV cameras facing out towards balconies and terraces in the building’s offices to deter intruders, according to a planning document from that time.

That has raised questions about whether the angle was deliberately changed, and if so whether that occurred during Hancock’s tenure as health secretary.

Regardless of whether the camera was tampered with, the revelation that there was a CCTV camera in a senior minister’s office has caused alarm in Whitehall and Westminster.

Sir Ed Davey, leader of the Liberal Democrats, said: “There is absolutely no need for CCTV in ministerial offices, and multiple arguments against. Ministers, officials and advisers can be debating and taking decisions of huge significance — and the danger of those being recorded and those records hacked must surely be greater than any security benefit from the cameras.”

Tom Tugendhat, the Tory chair of the foreign affairs select committee, said: “We need to know more about what this CCTV camera was doing. Cameras can be fitted with facial recognition software and used for commercial as well as state advantage, even if people are not able to listen.”

Julia Lopez, a Cabinet Office minister, tried to calm concerns telling MPs this week that the recording had not come from a “covert” bug and that the CCTV was thought to be an “outlier” — with other ministers not being monitored in the same way.

Emcor won a £22m contract in 2018 to provide “total facilities management services” for the DHSC and Care Quality commission estates. Labour has called for an urgent audit of government contracts after a report that it has also worked at sensitive sites including RAF bases and the Defence Science and Technology Laboratory at Porton Down.

The American company declined to comment on a claim that it wasnow a central focus of the health department’s investigation.

But earlier in the week it said it was “working closely” with the inquiry and officials said staff from the company are being interviewed as part of the process. The Metropolitan Police is not involved in the inquiry and has said “no criminal investigation” has been launched.

One security expert said the footage of Hancock is consistent with someone having initially filmed the CCTV using a smartphone.

“The footage shared by The Sun shakes slightly, which suggests to me that someone may have been filming this on their phone rather than exporting the file, for instance via USB, which would be easily traced by the IT team,” said Philip Ingram, a retired military intelligence officer.

In a further twist, Isabel Oakeshott, a political journalist, said on Thursday she had been offered the compromising images before The Sun by a businessman and lockdown campaigner who received the clip via the encrypted Protonmail messaging service.

She wrote in The Spectator that she rejected the clip because she thought it was a fake.

However it is not known whether The Sun obtained its footage through the same intermediary or directly.

Victoria Newton, editor of The Sun, has described the mole as an “angry whistleblower” who was furious that Hancock had been “breaching his own lockdown rules”.

Two people with knowledge of the situation have told the Financial Times that The Sun paid a large sum of money for the footage. And while the newspaper refused to comment when asked if it had bought the CCTV images, one former staffer suggested a payment in the “high five figures” would be the usual fee for such a big story.