Raising a child is an expensive business – but the cost of having children doesn't disappear when they turn 18. 

Last year, parents and grandparents in the UK spent a mind-boggling £18bn supporting their adult children and grandchildren – an average of £900 each.

Research from Post Office Money Savings revealed that nearly one in five Brits (18%) provided full financial support for their grown-up children. 

It also showed that many parents hold more than a third of their savings in a separate pot reserved for helping out younger family members.

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Post Office Money Savings found that day-to-day expenses were the most common thing for adults to have funded by their parents (39%) followed by holidays (32%).

Of those who have financially supported their children, around a quarter of parents (26%) paid for their children’s university fees and accommodation, while 24% gave them the money for driving lessons.

Just under a fifth (17%) helped pay off debts, 16% contributed towards a deposit for a new home and 12% chipped in towards mortgage or rental payments.

According to the research, parents and grandparents are often sacrificing their own finances in order to help out their children or grandchildren.

More than half (55%) dipped into their savings while 14% used a credit card. 30% stopped putting money into their own savings accounts and 7% even skipped paying their own household bills so they could help a family member.

Henk Van Hulle, of Post Office Money Savings, said: “Many of today’s millennials face an uphill struggle in establishing themselves as financially independent.

One of the most common ways for parents to financially support their children is to help them buy a car. Image by Michael Jung/Shutterstock

“Soaring house prices, the expectation they should be saving for retirement, and meeting day-to-day living costs can add up to significant challenges when it comes to managing their finances

“Our research shows that the majority of parents feel responsible for continuing to financially provide for their adult children even when they become an adult, as well as also providing for their grandchildren, totalling a huge £18bn a year.

“While it is understandable they want to help as much as possible, in some cases this is having a detrimental effect upon their own finances and ability to build up a savings pot.”

Three in five parents (61%) said they were happy to support their children financially but a fifth (18%) worry about this dependency. 8% actively resent supporting their children financially, the research found.

Mr Van Hulle said it is important that parents don’t sacrifice their own financial stability. “If people do want to support their children, it’s never too early to think about saving.

“Often it can seem impossible to put savings aside but whether it is on a little-and-often basis or taking advantage of a lump sum, people should do all they can to make sure they are making the most of their tax-free allowance before the end of the financial year in April.”