A while back, I asked a man at a party what he thought the secret of a happy marriage was. “One bank account,” he said without hesitation. “Keep it simple — what is yours is mine — that way there’s never any cause for guilt or resentment.” At the time I didn’t think much of it. Now, post-credit crunch, I find myself thinking about it all the time — that and the reaction of the woman who overheard his answer, rolled her eyes and said: “Keep your money private. You have to have some leverage.”

When the financial crisis hit, there were plenty of stories about the wives of the rich calling time on their marriages before the cash dried up. But now, as the dust begins to settle, it turns out that it isn’t only fat cats and their blonde trophies whose relationships were glued together by cash: 25% more couples in the southeast are seeking Relate counselling post the crunch, and Creditexpert.co.uk reports that 3.2m of us now have bank accounts that are kept secret from our partners. This seems like a pretty gloomy state of affairs. Then again, you could argue that the recession has provided a welcome reminder that marriage is still, despite all the modern emphasis on romance, an economic partnership. Who earns what, who pays for what in return for what, and whether both of you feel the deal is fair are crucial to every relationship. Yet confronting the fact that their destiny is roped together can be shocking for the generations who put off marriage, and were used to being financially independent before they tied the knot.

“I think it’s true that if you don’t have children, your independence isn’t really compromised when you get married,” says Ellen, who married five years ago, at the age of 30. “I wouldn’t say I keep my earnings secret from my partner, but he doesn’t know exactly how much I earn. For me, it’s about knowing I am not dependent on anyone. I like to know I could walk away if I wanted to — even though I never would. It’s just a way of avoiding feeling claustrophobic.” What if he was out of work and she had to look after him? “I’d do it, but I’d find it difficult.” And if it was the other way around? “I think I’d feel insecure relying on someone else.”

The trouble is that this “what’s yours is mine, so long as my life isn’t compromised” philosophy only works when there is plenty to go around. If one of you gets into financial difficulties, that urge to retain a degree of financial independence turns into something potentially sinister.

“I do put money aside now that my husband doesn’t know about,” says a media executive who wishes to remain anonymous. “He is more easy-come, easy-go than me, and that was okay when he was earning a lot more, but now I find it harder to let everything I am earning go into the pot. My sister asked, ‘What would you do if he needed that money?’ I would give it to him, of course. But I do think of it as mine. And I realise that’s not fair.”

It may not be fair, but it is perfectly natural. Some economists now recognise that behaviour relating to money conforms to a different set of rules from the ones that affect the rest of our social behaviour. Love and money don’t necessarily mix, because money taps into the part of our brains linked with survival, and we are rarely capable of treating it rationally.

There are more altruistic reasons for keeping your finances secret. “If I told my wife how much I was spending on my children from my first marriage, she would have a fit,” says a management consultant. “I’ve learnt from experience that what she doesn’t know can’t upset her. And life is much calmer as a result.”

There is no right or wrong way to deal with money in a relationship, but whatever way you choose to work it, both of you need to understand the deal. I have a colleague who was blasé about money, until her husband was between jobs last year and went out one day and bought himself a load of shirts. They had a huge row and the upshot was that they got rid of their joint account.

Maureen Rice, the editor of Psychologies magazine, believes that pooling your resources will always end in trouble because, she says, all couples require “financial space — ‘That is yours and this is mine.’ Having one joint account is crazy, because people naturally have different priorities. If he wants to spend a lot of money on football tickets and gadgets, it can drive you mad”.

Even if you are not earning, separate bank accounts are still the recipe for romantic harmony. Rice gives an example of a male friend who pays his wife an allowance in return for her staying at home and raising the children. “This isn’t patriarchal in my opinion. It’s about giving her financial space: that is her money to use exactly as she chooses. Think of your relationship as an account, with deposits and withdrawals, it’s about valuing housework and raising children as much as earning.”

Her advice in a recession is to try to keep that space, whatever your circumstances. Have an account for joint expenses, but don’t automatically share everything. “And, I hate to say it, you need to talk, because money brings out these primitive roles,” she adds. She is referring to the assumption that men provide for women and women are provided for: the paternal associations of money. So what happens in relationships where the woman earns more? “I thought it would alter the dynamic of our marriage,” says one woman who now earns twice as much as her husband. “But it works for us, because I’m happy to let him be in charge. I’m like the talent and he’s the manager, so I feel he’s putting in as much as I am.” She admits, though, that they had to sit down and confront the issue head-on. “I said, ‘We have to say if one of us is making the other one feel uncomfortable.’ I think that’s the key.”

So how do you protect your relationship from financial meltdown? By establishing the rules up front. By being open about your worries. By discussing problems as soon as they arise. The same rules, in other words, as apply to sex, fidelity, raising children, juggling work and domestic life. But, as an old girlfriend of mine says — in the end what really matters is that you have the same attitude to money. “I couldn’t be married to someone who was prepared to drive five miles out of the way to get cheaper petrol. To me, that thinking is much more damaging to a relationship than hiding money under the mattress. It’s not about the money itself, it’s about being financially compatible.” Something to think about, crunched or not.

Times recommends

• McDonald’s: the world’s local restaurant
• Help me to be a mum: a foyer to fulfilment
• A life online: God likes a laugh