Children costing parents £30,000 – after they are 18

The average parent expects to hand over 30,690 to their child during this period, covering everything from university tuition fees, to the deposit for a house, to day-to-day living expenses.

Around 93 per cent of parents with children aged over 18 said they were still providing them with some form of financial support, according to research for child trust fund provider The Children's Mutual.

Parents were most likely to be helping out their children with general living costs at 48 per cent, while 40 per cent let them live at home for free or for a reduced rent and 32 per cent were helping them with their bills.

Three out of 10 parents were paying university fees, 20 per cent had covered the cost of a wedding, 15 per cent had provided a deposit for a house and 14 per cent were repaying their child's debt.

But the burden of supporting their adult children was having a significant impact on parents' finances, with 28 per cent having to remortgage to cover the cost.

Two-thirds of parents said they had or planned to reduce their day-to-day living costs, with 28 per cent spending less on food.

More than half of parents said if they had known what a drain their adult child would be on their finances they would have saved more.

The Children's Mutual chief executive David White said: "No longer does turning 18 mean financial independence – in fact 16 per cent of parents questioned expected their child to remain financially dependent on them into their thirties and beyond."

1,484 parents were questioned for the survey.