I was 11 when she was elected, and it felt as though she'd sucked the clean air out of my universe. She made us all so mean-spirited. Even as a loud and proud feminist, I mustered only muted respect for her extraordinary and historic achievement of becoming Britain's first female prime minister. How could I respect someone who smashed the glass ceiling, only to reinforce it with concrete?

The nicest way I can put it is that she unwittingly brutalised an entire generation. But then again, I don't think she was unwitting, and we're clearly still picking up the pieces today. She trebled child poverty and infected our entire country with her misanthropic view that society didn't exist. Her actions eroded rights for women and the underprivileged every day in countless ways.

I sometimes ask myself if I can forgive Margaret Thatcher. Obviously I'm no Mandela. I've always found it hard to forgive gratuitous physical or social violence - the exception being when the perpetrators themselves have been brutalised. Show me evidence of Margaret Thatcher's childhood neglect or abuse, and I'll forgive her unconditionally. Until then, even 30 years later, I fear I won't. She sacrificed whole communities. And if hindsight proves she merely hastened the end of livelihoods that would never have survived the new century, the fact is, she did it with relish.

Yet I have to accept a bald fact. Margaret Thatcher was my role model. Throughout my teenage years I wanted to be - and was misguidedly convinced I would be - prime minister. A lot of this was down to Margaret Thatcher.

Maggie was the only thing in 1980s Britain that made a girl imagine she could grow up to be prime minister. She cleared the path for women (and men) to think that leadership was gender-neutral. Granted, the head of state was also a woman, but I had no chance (or desire) to grow up to be Queen. While Lizzie was a figurehead, Maggie was the real deal. And I was so sickened by Maggie, so desperate to oust her, that she guaranteed my lifelong passion for politics - the only means of getting rid of the occupant of No 10.

Long after I realised that being prime minister was neither feasible nor desirable, it was still my dream to work at Downing Street: I wanted to have some role, no matter how small, in ensuring that the policies coming out of government enhanced life chances, rather than stifled them. Thatcher had aroused such deep hostility in me that I became shaped by my struggle against her. If she hadn't existed, I may never have become an MP. And the first parliamentary bill that I tabled in the House of Commons would never have been to reverse her hated compulsory competitive tendering - a typical Thatcherite innovation that outlawed equality of opportunity and made things harder for low-paid workers, particularly women.

Last year while working at Downing Street, I continued to cover the equalities brief. On one occasion I was accompanying Gordon Brown after a meeting at Westminster with MPs. As we drove slowly through the House of Lords car park, we passed an old woman struggling to get out of a passenger seat. Gordon was nearest to her, but was rifling through papers for his next meeting. The old woman seemed to stand to attention at the sight of the car and waved almost bashfully towards us, evidently assuming we might stop and speak to her. When Gordon didn't look up, her eyes slipped past his and, momentarily, locked on mine.

"Gordon," I said, still surprised to have looked so closely into those eyes, "you've just blanked Margaret Thatcher."

He seemed uncomfortable. "D'you think we should go back?"

I looked at the woman, who stared after us, the woman who had shaped my life and my country.

"No."

It was the most charitable thing I could think to say. And I couldn't help but watch with some small satisfaction as she faded from view through the back car window.

If my reaction was mean-spirited, then all can say in my defence is that, no matter how hard I try to escape, part of me remains, emphatically, of the Thatcher generation.

Oona King is a writer, broadcaster and political campaigner