When the story first broke last weekend that a secret list of “sex pest” Conservative MPs and cabinet ministers drawn up by researchers was circulating in Westminster, I decided to talk about my own experience of being lunged at by a Tory MP. By publicly discussing how it felt to be in that position, and how it was not acceptable, I thought it would help others to come forward to report sexual harassment. Yet because my incident happened 14 years ago, I decided not to name the MP in question.

A week on, things have changed. The MP has denied some allegations against him, and minimised others as somehow acceptable because they date from another time. His lack of contrition has made me change my mind. It is time for me to say publicly that the MP who lunged at me was Sir Michael Fallon.

At the time, I was a 29-year-old junior political reporter at the Daily Mail. He was a Conservative backbencher in his 50s and, as a member of the Treasury select committee and a former minister under Margaret Thatcher and John Major, a useful contact to take out for lunch. As a political journalist, I went out for lunch with MPs as often as three times a week. It was part of the job. But, over the hundreds of these encounters over my 14 years in the lobby, this was the only time an MP crossed the line – and that is why I remember it so vividly.

We ate at Quirinale, an upmarket yet friendly Italian restaurant five minutes’ walk from the Commons. We gossiped about rising Tory stars David Cameron and George Osborne. We drank wine – a couple of glasses at most. On the walk back to parliament, we had to cut through a quiet ante-room just off Westminster Hall before going to our offices. It was here that Fallon lunged at me. This was not a farewell peck on the cheek, but a direct lunge at my lips. When I have previously written about this incident (referring to an unnamed MP) I have described it as a “kiss” – but a kiss suggests something romantic, consensual. This was anything but. I shrank away in horror and ran off to my office in the press gallery. I felt humiliated, ashamed. Was I even guilty that maybe I had led him on in some way by drinking with him? After years of having a drink with so many other MPs who have not acted inappropriately towards me, I now know I was not.

I did not report Fallon to the Conservative whips, because I – as someone who had only been in the lobby for two years – was worried I would be blacklisted as untrustworthy. In Westminster, where power and loyalties are hard currency, I feared making enemies. Whenever I saw Fallon after the incident he did not act inappropriately again, but I knew that his previous behaviour, and my silence, had changed utterly the power dynamic between us. He had violated what should have been a healthy working relationship, turning it into something seedy and unpleasant.

Fourteen years on, I agonised over whether to come forward. It was an old incident, but I heard about more recent allegations involving Fallon. Having spoken generally about an unidentified Tory MP, I was already being criticised by some for not just giving him a slap. Then, on Tuesday the Sun broke the story that Fallon had admitted to repeatedly touching the journalist Julia Hartley-Brewer’s knee at a conference dinner 15 years ago. I do not want to criticise another woman’s response to harassment, but, in the ensuing coverage the impression was being left that this was a one-off incident that could now be laughed off. I knew that by failing to act I was letting down not only my 29-year-old self, but also any other women who may have been subjected to the same behaviour since. More importantly, I would be failing to protect other women in future.

When the Westminster harassment story had first broken five days earlier, I was hopeful we were going to have the same catharsis as Hollywood in the wake of the Harvey Weinstein revelations. I was in awe of the bravery of the young Labour activist Bex Bailey who had come forward to reveal she had been raped by a man at a Labour event. But the debate about the so-called “grey areas” – the groping of knees, the unwanted lunges – was turning into a trivialised farce about “kneegate”, as if everything up to rape was not something to get upset about. Fallon seemed to be getting off the hook. And so, at 5pm on Wednesday afternoon, I contacted Downing Street to report the 2003 incident to one of the prime minister’s aides. By 7.30pm, Fallon had resigned, admitting his behaviour towards women in the past had “fallen short” of the high standards of the armed forces.

In my conversations with No 10, I asked for a commitment that my name would not be revealed, which they respected. I still feared recriminations, not only from Fallon’s supporters in the Conservative party but from parts of the media. I watched in horror at the character assassination by the Daily Mail of Kate Maltby, the journalist and academic who had shown bravery and dignity in coming forward to make allegations about the first secretary of state, Damian Green, which he has strenuously denied.

But I was also appalled that, in an interview with the BBC’s political editor, Laura Kuenssberg, on Wednesday evening, Fallon showed little contrition. Asked if he would apologise for his past behaviour, he said all MPs would have to look back at themselves. He said that “what might have been acceptable 10, 15 years ago is clearly not acceptable now”. But just because my response 14 years ago was to run away, rather than telling him off, it does not mean I found it acceptable. Even his comment about the high standards of the forces seemed to minimise what he had done, as if he was somehow having to meet a higher bar than fellow MPs who could get away with it.

When it emerged, late on Thursday, that the Commons leader Andrea Leadsom had complained about lewd remarks Fallon had made to her, the former defence secretary denied it. Once again, some were dismissing the remarks as trivial, the sort of banter that goes on in workplaces across the country. By continuing to stay silent now, I was still running away from Fallon, just as I ran away from him in 2003. I decided it was time to come forward and name him. I want him to know that, however long ago this incident was, his behaviour was unacceptable. All I ever wanted was to be treated with respect. But even if he feels he cannot apologise to me, at least by coming forward I have redressed the power imbalance between us. I am taking back control.

Jane Merrick is a freelance writer and the former political editor of the Independent on Sunday