The venue she has chosen could not be more of a contrast to the woman herself. With the exception of a lone dragon tree wilting over the air-conditioning unit, the room at the heart of Conservative party headquarters in Millbank, central London, is self-consciously colourless: white walls, white plastic chairs, white tables.

The opposite is true of Margot James, the dazzling, millionaire vice-chairwoman of the party. She cuts a striking figure: almost 6ft tall, in skinny jeans and a pastel-pink designer jacket, a blonde bob framing a heartshaped face. Her only jewellery is a ring with two diamonds so huge that it is hard to take your eyes away from them.

James is a lesbian and is fed up with everyone banging on about her being a glamorous gay. For one thing, she is trying to win a parliamentary seat and fears such labels will put off voters. “I’ve always been honest about my life but it gives me no pleasure to be known for it,” she says.

“Being a lesbian is not really a selling point, is it?”

Perhaps not, but her looks and sexuality certainly make her stand out from the crowd. She is one of only a handful of gay female politicians. And none of the others is Tory.

“It is a shame, because I think role models are important,” she says. “As a teenager, if you are concerned about your sexuality, it is important to see that the stereotypes are not necessarily true. I remember crying when Martina Navratilova won Wimbledon and ran up to embrace her partner. It was an emotional moment – the idea that someone would be so open about such a relationship was very moving to me.”

She says she realised “quite young” that she was gay. It is clear that coming out involved a good deal of heartache, but she is reluctant to go into details for fear of sounding self-pitying and fuelling the interest in her private life. “It just sounds so sob-story-ish. I don’t want to put myself over as a victim.”

She is charged by David Cameron with working out what the party needs to do to attract young female voters. At the 2005 general election, only 22% of women aged 18-34 voted Tory.

Within two years she is likely to be an MP – Stourbridge, West Midlands, where she is the candidate, has a Labour majority of only 407 – and on a fast track to the cabinet if the Tories win power.

She tells me that she has been the victim of a smear campaign in the constituency, conducted through “cooked-up letters” in her local paper. “One in particular galled me. It went on about the ‘lesbian millionaire’ thing and asked: how can such a person reflect David Cameron’s family policies? I was so angry about that, because family is everything to me, actually. I don’t have children of my own, but I have nephews and nieces to whom I’m very close.”

James lives in a house in South Kensington, west London, with her long-term girlfriend, Jay Hunt, who runs a books and films business. Those who have been to their home say the interiors are all smooth browns and creams, with splashes of animal print and glitter.

James is protective of Hunt’s privacy and clearly uncomfortable discussing their relationship, although she hints they are unlikely to follow in the footsteps of Alan Duncan, the gay shadow cabinet minister, and have a civil partnership. I sense that the suggestion frustrates her, in the same way that some cohabiting heterosexual couples resent pressure to get married.

Her career began in the wine trade but took off when she went into public relations, setting up a company that became Europe’s largest PR firm in the healthcare sector.

When she sold it, her share of the proceeds was “around £4m”. Her self-made wealth has also been the subject of barbs in Stourbridge, with a whispering campaign that she is the sort of woman who spends £2,000 on a Prada handbag.

“I’ve never spent that type of money on accessories. Never would,” she says indignantly. “I’ve actually only got two handbags: one for summer, one for winter. Lots of women have far more than that.”

She is 50 but looks at least 10 years younger. I ask if she has had Botox and although she bats away the question, she looks a bit sheepish. She does not deny that her youthful looks don’t come cheap.

“I would be too embarrassed to go into my regimen,” she says. “All I’ll say is I’m horrified by the things you have to do to yourself as you get older to have any fighting chance of looking your age, never mind 10 years younger.”

Whatever her secret, she is keen to dispel any impression that she lavishes money on frivolous things. Her black pumps are Prada, but she is wearing the same jacket she had on when we last met.

“I’m not materialistic, certainly not. I’m quite careful with my money. My mother really taught me the value of money,” she says. “When my parents became well off, they retained their good values – they used the money to travel and educate themselves, not just to buy things.”

Her political enemies would have voters in Stourbridge believe that she is a Londoner who has been parachuted into the seat. In fact, she grew up nearby in Coventry. Her parents were “proud working-class people”. Her father, a successful entrepreneur, used to regale her with a tale of coming to London “with sixpence in his pocket”.

At seven, she was sent to boarding school, where she was an incorrigible rebel. Two schools expelled her – the first for being disruptive, the second for going to a pub – but her elder sister married a man who turned James’s life around.

“When I was 15, my brother-in-law, whom I really looked up to, read my end-of-term report, which was dire. He took me aside and told me it had got to stop. He said I was going to ruin my life.

“I was so used to being the bright spark who played the fool, but he believed in me; told me I could do more. I didn’t want to let him down. After that, I discovered the joy of learning.”

She became interested in politics, idolising Margaret Thatcher. So she bunked off school to see her heroine arriving at the Commons as prime minister for the first time. “I saw her come out of St Stephen’s entrance and found myself shaking her hand,” she recalls. “It was an extraordinary thing for a woman to be leader of a political party in Great Britain; that was such a thrill.” These days, she often finds herself in the same room as Thatcher, who was recently guest of honour at a party fundraiser that James hosted at Michael Portillo’s house. She found herself escorting the Iron Lady around the room. “She’s frail but she exudes the same passion and power as she did in the old days,” James says.

Besides encouraging more women to enter politics, James campaigns on healthcare – a priority for women voters. She is battling an “awful injustice” she says she has unearthed in Stourbridge, involving a drug that prevents age-related macular degeneration, a cause of blindness. The primary care trust has refused to fund the treatment for this common condition, condemning hundreds of pensioners to lose their sight, she claims.

“Their policy is chilling. They say preventing things like falls, depression and immobility does not ‘release cash’. So they just let them go blind.”

James also has strong views on law and order, warning that the Tory party must not “throw justice out with the libertarian bath water”. She admits that she admired Jill Saward, the Ealing vicarage rape victim, who stood against David Davis, the former shadow home secretary, in the by-election he called to provoke a debate on civil liberties. “I am concerned that some of the key weapons the police have in their fight against crime are starting to get rubbished as part of the surveillance society,” James says.

“The publicity around that by-election could undermine some of the important things I feel could protect our liberty, like CCTV and DNA testing. I would not want those things to get a bad image. Antisocial behaviour is the number one concern in Stourbridge and I’m sorry but people want more CCTV – not less.”

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