Are bills ruining your family life? Try the lover's guide to coping with debt...

If an unexpected envelope arrives on their doormats today, many people will fear it is a bill rather than a Valentine's card. But, if you are in one of those relationships where debts loom larger than love, some new statistics, given exclusively to The Independent, might help you.

It is entirely normal for relationships to suffer when households have problem debts, according to research from CAP (Christians Against Poverty) which polled 1,700 of its clients. Three out of four couples with money worries (76 per cent) say debt has caused them arguments. And one in five couples (21 per cent) said debt led to relationship breakdown.

The good news is that there are free debt advice centres around the country that can help couples assess the level of their debts and be open with each other. This approach might sound too simple to work – but experts at CAP and a couple we spoke to who survived problem debt (see box, right) believe that talking with each other has to be the starting point. When asked for his tips for couples with debts, CAP debt specialist Dave Tudor replies, simply, "Talk." He then adds: "Anything which is under wraps damages you internally. It creates mistrust."

So what other evidence is there about the extent of relationship problems related to debt? It is the source of "one of the biggest strains on a relationship", according to Relate, the counselling charity. It was the most widespread worry, cited by 62 per cent of respondents, when Relate conducted research last year – easily beating the other main causes: poor work/life balance (40 per cent) and infidelity (36 per cent). And older folk (69 per cent of the over 65s) are more concerned about money harming their relationships than younger people (37 per cent of 16 to 24-year-olds), according to the same Relate survey.

Getting into debt that we struggle to repay often has direct effects on our approach to communicating with others, says Dr Rob Waller, a consultant psychiatrist in Scotland. "Debt causes depression," he says. "Depression causes people to isolate themselves and that's not good for relationships."

Arguments between parents – or cold silence – can also affect the relationships they have with their children. "Debt has a really severe effect on children," says Sam Royston, head of policy at the Children's Society. "Children are more likely to be caught up in arguments." A quarter of parents feel that children are more likely to become anxious or stressed if their family has problem debts, according to Children's Society research.

The situation where a couple has debts is usually harder to deal with – "more complicated, with more issues" – than that when a single person has debt, according to Dave Tudor, CAP's regional manager in the North-west. People living together as a household need to collaborate to get out of the debt, he says. That means opening up about what they both owe, working out a way to deal with debts and setting up a budget in order to go forward.

But couples often go through a major transformation when the partners open up to each other. Problems that seemed impossible can be solved. A major issue for many families is not letting down the children. But, contrary to what parents might expect, Mr Tudor suggests that if the kids are of a certain age, it's best to get them involved. "Once kids have understood, the pressure release is enormous. The parents don't have to perform any more – and the kids know that love isn't an issue." If children are not told, he warns, they can notice that birthday presents, for instance, get smaller and they can take the interpretation that they are not loved any more.

National Debtline takes a somewhat different approach from CAP on the relationship issue and does not see it as such a hurdle if one member of a couple does not want to tell the other about a debt problem. Laura Mostaghimi, an adviser at National Debtline, does say, however: "Normally, someone has more options open to them if they tell the other one." They will have two sets of resources, for instance, and can use their shared assets as well.

Telling the other partner can be "quite stressful", she says. "Normally, the person who ran up the debt is quite reluctant to tell the other one – because they want to sort it out on their own." For instance, Ms Mostaghimi has recently been helping a woman who has £15,000 of debts but does not want to confess to her husband, even though he earns a lot more than she does.

There are also many cases where both partners have debts but one takes a more rigorous approach to clearing them than the other. What can help in these situations is the obvious move of making sure that the less willing partner also speaks to the debt adviser. This approach can have a positive effect in making that person more focused, says National Debtline.

Advice from Relate suggests that relationships are well worth fighting for and can make us stronger. In its report last year, it said: "Strong relationships are our best asset when coping with the challenges that modern life throws at us."

CAP: capuk.org and 01274 760720

Children's Society: childrenssociety.org.uk/about-us/contact-us

National Debtline: nationaldebtline.org/EW/Pages/default.aspx and 0808 808 4000

Relate (relationship counselling): relate.org.uk and 0300 100 1234

In the small town of Eaglescliffe, on the north bank of the river Tees, Ray and Patti Penn will today celebrate 11 years together. And, considering what they have already suffered and seen off, they can probably be very confident that their relationship will endure.

Debt nearly destroyed their future together. Back in February 2004, when they first met, Ray was earning £40,000 a year, teaching corporate computing at the University of Leeds.

Patti, however, was suffering long-term neurological problems – and, when Ray became unwell too, the combined health problems of the couple meant that in 2005, Ray was at home looking after Patti and bringing back just £3,000 a year in Carer's Allowance.

They both also had debts.

Ray thought he owed about £2,000 on credit cards, bank loans and other agreements – but that turned out to be a major underestimate.

Patti owed £35,000. "Neither of us really knew what the other owed," says Ray. "For the first few years, you don't really want to tell your partner that you are massively in debt."

Nor do people want to discuss previous partners – and, for Ray and Patti, both their debt burdens had been built up with their exes.

For seven years – sometimes getting 40 phone calls a day – they laboured on, shuffling debts, keeping their fingers crossed, not addressing the issues and becoming more stressed.

"We had some humdingers of arguments," Patti says. "And you would feel guilty, but it wasn't really your fault. And there was nothing you could do." But the situation became so bad that it pushed them into resolving it. Ray had a nervous breakdown in October 2011. "I was very, very delicate," he says. "It took hardly anything to wind me up. I was incredibly angry with anyone and everything."

Some of Patti's friends urged her to leave him. "But she stood by me."

A friend worked at CAP, the debt charity run by Christians Against Poverty – and Patti, although reluctant to take her problems to a friend, went to see her "out of pure desperation".

But as Ray had two more breakdowns within the next few months, the couple realised that they had to act. It was only at this stage that he discovered that he had debts of £11,000.

He went to counselling sessions with a friend. And he and Patti went on a "discovery break", a spa weekend away put on by CAP so that they could relax and relate to each other as a couple again. Self-help sessions were put on – and Ray felt stronger after attending two about forgiveness and anger management.

With the help of CAP, Patti went bankrupt and Ray went through a lighter version of that, a Debt Relief Order. "It allowed us to stop, breathe, realise you are still breathing and that you have a partner," Ray says. They drew up a household budget with CAP, and this included a small savings plan. "Money was very tight," says Ray. "It leaves you with a food allowance. But we were used to being without money."

When they got through the bankruptcy and Debt Relief Order regime, they discovered that they had also managed to save up £1,000 under CAP's budget. And they decided to get married – which they did on 7 June 2013. They would give similar advice to any couple in the same situation: "If you have got a CAP centre near you, just talk to them," Ray says. "Don't be embarrassed: just talk," Patti agrees.