Gavin Williamson, the defence secretary, has refused to answer a series of questions about the circumstances surrounding a relationship with a colleague which he disclosed in a Daily Mail interview.

Williamson, who has been tipped as a future prime minister, gave the interview during a day of frenetic activity during which he also made a keynote speech to parliament and raised eyebrows with an interview in the Daily Telegraph in which he said Russian cyber-attacks could leave “thousands and thousands and thousands” of Britons dead.

The Mail interview was published a few hours after Williamson’s lawyers refused to answer a series of questions from the Guardian about his departure from the fireplace firm Elgin & Hall, where he was the managing director in 2004.

In the article, he said the relationship “became flirtatious and a couple of times we shared a kiss”. He said he decided to leave the company to save his marriage to Joanne, a former schoolteacher.

However, a number of sources have suggested a more complicated story.

In a series of exchanges that began on Thursday, Williamson’s lawyers refused to say:

Whether the woman reported Williamson’s behaviour to her line manager and an internal process followed.

What the outcome of that process was.

The terms on which he departed and whether he received a pay-off.

Whether it was right for a managing director to engage in a relationship with a junior colleague.

Why there appears to be no mention of his employment at Elgin & Hall in his official profile or social media.

Interviews with former employees from the firm and its parent company, Aga Foodservice Group, established that the woman who became involved with Williamson was a junior manager.

Williamson has had a meteoric rise in parliament from backbench MP to his current cabinet position as secretary of state. He has recently waged a public campaign against the Treasury to secure more money for the armed forces.

He was promoted from chief whip to defence secretary in November after the then incumbent Michael Fallon’s resignation for making sexual advances towards a journalist in 2002.

His promotion angered Conservative MPs who claimed he had a hand in forcing Fallon from office and view the whips’ office as the problem at the heart of covering up sexual harassment and abuse – a claim he has denied.

Other colleagues, including the environment secretary, Michael Gove, have this month tipped the MP for South Staffordshire to be a future prime minister.

The alleged incidents at Elgin & Hall took place in 2003 and 2004 after Williamson was recruited as managing director. The firm was then based in Bedale, North Yorkshire, where Williamson was in charge of a team of more than a dozen office staff.

Williamson told the Daily Mail the relationship began after he and the woman travelled together on company trips.

“[It] became flirtatious and a couple of times we shared a kiss. It never went further than that, but this had a profound impact on us both and those close to us,” he said.

He added that he left the firm after telling his wife about the relationship. “Going back to work afterwards it could never feel the same,” he said.

Informed sources said events came to a head in the summer of 2004, when the woman told her direct line manager about her working relationship with Williamson.

A meeting was held to discuss the issue with senior executives from Aga, it is claimed. Days later, former staff claim, Williamson left the company and the group with no explanation. Aga declined to comment.

Articles about Williamson have made much of his decision to find work in business after leaving university rather than pursue a job in politics.

Until Thursday, there had been no mention of Elgin & Hall or Aga in his official website profile or in newspaper articles. Company sources claim that Aga had previously employed him as a sales manager in another subsidiary firm.

Williamson has been promoted as “the baby-faced assassin” in a series of newspaper articles which have compared him to Francis Urquhart, the ruthless and ambitious central character in the UK political thriller House of Cards.

For three years he was David Cameron’s parliamentary private secretary until the former prime minister’s resignation following the EU referendum.

He was promoted from backbencher to chief whip by Theresa May in 2016 after choosing to back the then home secretary rather than Boris Johnson in a leadership contest.

His position as a key May ally was cemented when he was chosen to negotiate with the DUP over a “confidence and supply agreement” in June.