The insurer warned that two-thirds (67 per cent) of those married, cohabiting or in a civil partnership, and splitting the rent or mortgage, would struggle to keep up with their payments if their partner were to stop contributing towards the bills.

Direct Line found that, on average, partners split their home payments fairly equally, meaning that if one person was to stop being able to pay their share, the cost for the other would be substantial.

The average monthly mortgage repayment across the UK is £581, which is 18 per cent of the average disposable household income amount (as calculated by the Office for National Statistics).

Should one person not be able to pay their share of the mortgage, the remaining partner would need to find an extra £291 per month to cover the remaining half of the mortgage, and the overall cost would become 36 per cent of their disposable household income. Direct Line warned that many people would not be able to cope with this extra cost.

For those renting, the average cost is even higher. According to the HomeLet Rental Index, the average rent in the UK currently stands at £889 per month, equivalent to 27 per cent of the disposable income per household. Should one person be left to cover the rent themselves, they would need to find an extra £445 per month, equivalent to 54 per cent of their disposable household income.

For nearly 4 million people (28 per cent), it would be impossible to find this extra money based on their income alone and they would immediately be unable to keep up with their home payments.

Only around a fifth (22 per cent) would be able to continue paying their rent or mortgage without their partner’s contribution. While this rises slightly for men (27 per cent) and falls for women (19 per cent), it shows how reliant people are on their joint finances and how much they would struggle if something was to happen to their other half.

If the worst was to happen and their partner passed away for example, nearly half (44 per cent) of those with mortgage or rent payments – more than eight million people – would potentially have to sell their home or move to somewhere with lower rental payments due to their reduced income. Despite this risk, more than six million people (34 per cent) don’t have any form of financial protection in place to help protect their home in the event of losing income.

The most common form of protection is life insurance, which just under half (46 per cent) of those with rent or mortgage payments have taken out, and death in service benefit (24 per cent).

A fifth (21 per cent) of those questioned had critical illness cover, which provides a tax-free lump sum to help pay for a mortgage, rent or debts in event of a serious illness. Just over one in 10 (13 per cent) are covered by income protection, which provides a regular income in event of illness or injury.

Worryingly, there are currently over five million couples across the UK with a mortgage and no form of life or illness protection to support them should one partner pass away or be unable to work due to illness.

Jane Morgan, business manager at Direct Line Life Insurance, said: “It is understandable that we rely on the finances of both people in the relationship to pay our mortgage and rent. These are expensive outgoings which often need two incomes and it probably feels like we would never need to worry about paying their share.

“Unfortunately, it’s impossible to know what will happen in the future so it’s important to be prepared so that if the worst does happen you know you are able to carry on paying your bills and don’t have to worry about moving home. Nobody wants that kind of additional worry during an already very stressful time of their life and life insurance could offer important financial protection and peace of mind that you’d be able to stay in your home through a difficult time.”