A heterosexual couple are launching a legal bid to become civil partners. What's their problem with getting married?

Just like any young lovers, Tom Freeman and Katherine Doyle are thinking about their future.

After five years together, the 26-year-olds are planning their life ahead and, naturally enough, they want to formalise their relationship.

For many straight couples in their position, the next steps would be obvious: get engaged, send out the invites to all their friends and family, put in the order for the champagne, then head down to the church or register office for a wedding.

But Katherine and Tom aren't most couples.

They don't want to get married. But they still want to make a lifetime commitment to each other. And they'd like greater legal and financial security than that offered by simply cohabiting.

So what's the solution? It's obvious, really: a civil partnership.

There's only one snag. Under the Civil Partnerships Act 2004, such arrangements are restricted to couples of the same sex.

This, however, is not enough to deter Tom and Katherine. So on Tuesday 9 November, they will head to their local town hall in Islington, north London, and file a civil partnership application.

How to propose a civil partnership Simon Fanshawe, author of The Done Thing: Negotiating the Minefield of Modern Manners Civil partnerships are a bit like second marriages: the couples have usually lived together beforehand, so when one is proposed it's often a case of, "Do you think we should?" "Oh, OK then." But it's perfectly acceptable to say, "Will you marry me?" People talk about weddings when they mean civil partnership ceremonies and refer to their husbands or their wives. It's part of the culture now. I support gay marriage, and while civil partnerships were right for their time I don't see the point of extending them to heterosexuals. Then again, I suppose you could always get down on one knee and ask: "Do you want to merge our tax affairs?"

It is part of a legal bid spearheaded by the activist Peter Tatchell called the Equal Love campaign, which aims to redress the imbalance between heterosexual and homosexual partnership rights.

Katherine and Tom will be one of four straight couples who will apply for civil partnerships. As part of the same process, four sets of same-sex couples will attempt to sign up for marriages.

Working on the assumption that all eight will have their bids rejected - an earlier attempt by Katherine and Tom to register for a partnership failed in 2009 - Equal Love plans to launch a legal challenge on the basis of human rights legislation.

Whatever your views on the issue, the argument that gay and lesbians should be allowed to marry is straightforward enough to follow. Civil partnerships, which came into force in 2005, mostly give same-sex couples the same legal rights as married couples, but some campaigners believe the arrangement lacks the status enjoyed by marriage.

It is a viewpoint that has gained cross-party backing, having become official Liberal Democrat party policy and received the backing of Labour leader Ed Miliband and Conservative Mayor of London Boris Johnson.

But why would a straight couple demand the right to be joined in a civil partnership that so many in the gay rights lobby believe is inadequate?

Both Tom and Katherine explain that their primary reason for not getting married is that they do not want to be part of an institution from which gay and lesbian people are excluded.

CIVIL PARTNERSHIPS: KEY FACTS Image caption The French version of civil partnerships have proved popular with straight and gay couples alike Legally recognised union between a same-sex couple

Equal legal treatment in matters including inheritance and next-of-kin arrangements

Marriage ceremonies must be public and can be conducted by clergy

Partnership can occur in private `

Failed partnerships require a legal dissolution, like divorce

Political, religious and social considerations influenced legal title of the union

Most campaigners accepted title because they had secured the underlying rights Q&A: Civil partnerships explained

But they say that, even were the law to change to allow same-sex marriage, they would still choose to have nothing to do with it.

While many young women dream of the day they walk down the aisle as a bride, Katherine, a postgraduate student, is not one of them.

"For Tom and I, the role of the husband and the role of a wife seem very strict and that's not for us," she says, arguing that such categories derive from an era when women were subservient to men. "In our day-to-day life, we feel like civil partners, not a married couple.

"There's supposed to be something transformative about marriage, but a wedding wouldn't change our relationship."

Tom, a civil servant, agrees. "We don't feel like a husband and wife, we feel like partners," he says.

The couple argue they are discriminated against because heterosexuals who eschew matrimony receive none of the tax breaks enjoyed by either married couples or civil partners.

Indeed, Peter Tatchell argues that current civil partnership arrangements are "heterophobic" on the same terms that he believes the existing system of marriage is homophobic.

The system, he insists, is one of romantic "apartheid" which only serves to divide people, and he believes even civil marriages cannot accommodate those who want to shake off the institution's historical association with property rights.

"Some [straight] women don't like the whole history and baggage that goes with marriage so they find civil partnerships attractive," he says.

"This isn't a gay rights campaign - it's about equality for everyone."

With marriage, it's been shaped by the fact that it's usually been between a man and a woman Mark Vernon, Writer and philosopher

If the campaign sounds novel to British ears, it would be considered retrograde in France, where the equivalent of civil partnerships have been available to gay and straight couples alike since 1999.

In 2009, some 95% of those taking up the pacte civil de solidarite (Pacs) were heterosexual.

And while the number of straight French couples opting for Pacs has risen, the number of marriages has shrunk, to the point that there are now two couples entering into a Pacs for every three getting married.

It is a statistic that Equal Love supporters would use to assert that many heterosexuals want the legal security of a civic union without the historical and cultural baggage of marriage.

But by the same token, advocates of traditional family values could use the same figures as proof that straight civil partnerships undermine married life as an institution.

Not all opposition to Tatchell's campaign comes from such quarters, however.

Writer and philosopher Mark Vernon is himself in a civil partnership, but believes that it is correct that the law recognises the differences between gay and straight relationships.

The author of The Meaning of Friendship, he argues that heterosexual couples, whether they like it or not, cannot escape the gender roles framed by centuries of marriage. Likewise, he says gay couples should embrace the opportunity to define civil partnerships on their own terms.

"When you get into an institution you buy into a whole history, like it or not, and with marriage it's been shaped by the fact that it's usually been between a man and a woman," he says.

"The idea that by having a civil partnership rather than a marriage you can circumvent that is self-deluding. I would have thought that you'd be better off reshaping the institution of marriage from within."

Whether one supports their campaign or otherwise, surely everyone would raise a glass to Katherine and Tom as they prepare for their life together. For richer or for poorer, for better or for worse.