Michael Winner spent most of last week thinking about my breasts. If I were posting this on Twitter, I would add the hashtag #SentencesINeverExpectedToWrite.

Last Sunday, the Observer ran a feature about five years of Twitter, in which I had a quote about how much I love its community spirit. I had no idea I was about to become one of those people who have a huge Twitter row with a celebrity. How weird.

It started when someone using Michael Winner's name posted on the site: "IT suggests I follow Victoria Coren. Who the hell is she? Y should I follow her? Her tweets read dull."

This was obviously somebody posing as Winner. His other posts were peculiar, so badly spelt as to be almost incomprehensible, with only 6,500 followers. They weren't very funny. The impostor was evidently a bit simple, motivated only by desire to make Michael Winner look like an idiot. He has a daft image already, but I'd always felt rather fond of him from afar.

This impostor then wrote to me (publicly, via his page): "VICTORIA ALL MY TWEETERS RIVETED BY YOUR BOSOMS."

He wrote to someone else: "NOW I KNOW SHE HAS LARGE BOSOMS." To another: "If you're not clear if Victoria's bosom are firm, go there and get a hold on the situation."

He sent a direct private message, just to me, saying: "You have enlived my tweeters who discovered your breasts when I knew 0 about them." He put up four more public posts about my breasts and chatted about them with all who passed by – wheezing happily to one follower: "How naughty of Uto suggest Victoria shows us a piccy-poo of her boobs." Just feel the dribble of saliva on keys.

Then somebody sent me a link to an official Twitter listing on the Times website. This wasn't an impostor at all. It actually was Michael Winner.

What a bizarre twist. Actually Michael Winner, hunched over the keyboard, typing incessantly about my bristols? Is he getting dementia? I've been playing poker in casinos and dodgy clubs for 15 years, I'm familiar with dirty old men who think it's hilarious to shout: "Show us your tits!" across a room, but it's not usually a national treasure doing it in a public place. Michael Winner was shouting: "Show us your tits!" in front of nearly 7,000 people. I didn't think he should be strung up, just helped quietly to a chair and given a nice cup of tea.

Later that evening, @jpdhavers tweeted that Winner's account had been hacked. Of course! Nobody with a public profile, even one as ridiculous as Winner's, would put his name to such icky unpleasantness. I found Winner's number (not hard; he loves to be available for journalists) and phoned to warn him about the hacker. A woman answered and said he wasn't at home.

The next morning, his page said, over three furious tweets: "At 10.25pm last night, waking both me and Geraldine went 2 bed early cos of jet lag, on the phone to my home – Voictoria Coren. Appalling! Vicgtoria Coren has bno manners to phone people at 10.25pm, not urgent, she asked Geraldine who answered if my twitter had been hacked in to. Victoria Coren is RUDE. I don't know her, don't want to know her, won't speak."

At that point, no doubt remained. The astonishingly real Michael Winner added that I have "no manners, grace or charm". This from a chap who tweeted all day about a stranger's breasts. Clearly, we went to different finishing schools. (He also complained that I was "insiderate". It was like having a row with James Joyce. Except, really not.)

I apologised for the late call, but got no apology back. By now, everyone on Twitter was joining in. I had some lovely, kind, reassuring and funny messages; my favourite was from @janinegibson: "You seem to be feuding with what comes out of Michael Winner's blackberry when he sits on it."

But there were others: dozens and dozens from men telling me not to be so hysterical. I'd only tweeted a couple of bemused jokes. Is this fall-out from the sacking of Andy Gray and Richard Keys? It seems there is a large community of men so desperate to shout about women's breasts, so terrified of not being allowed to, that they complain about strident anger even when it isn't there.

I was angry only once, when Winner referred to my late father as "strane". Through the semi-articulacy, I knew this was not a compliment and my small fists clenched.

Also, of course, I felt embarrassed and sad. I can bluster my way through a comedy feud, but I'm not a stripper who confidently offers her assets for appraisal. I'm a writer, with an imperfect, private body. It was embarrassing to have a thousand people sharing public opinions about my chest. Winner tweeted merrily with a fan who wrote: "That's Victoria Coren's tits sorted. Piers Morgan should be our next victim."

So nasty and yet so ludicrous. A Twitter spat with Michael Winner? Who could take it seriously? I'm a grown-up girl, I've heard worse. Far worse – I've played poker with John McCririck. But what about the women who aren't pre-gruelled by years in a macho gambling underworld?

How does Michael Winner treat a nervous 23-year-old waitress when he's showing off in the Ivy? What does he say about the daughters of his friends? And these critical men who rush to defend the principle of dirty personal remarks; how do they behave around girls who are more timid, less articulate, less battle-weary than I am?

I didn't think Gray and Keys should be fired. I think free speech is all and humour is the best defence. But I do wish some people found it easier to understand what's funny and what isn't.

www.victoriacoren.com