Half of the 1,000 parents surveyed by the Money Advice Service said they underestimated the costs of caring for their first baby in the first year.
The research, conducted among parents with children under 10 years old, revealed that of the 50 per cent who underestimated how much they would need to spend, 61 per cent spent up to £1,000 more than they had planned, and 22 per cent were hit with between £1,000 and £5,000 in unexpected costs.
It's not just first-time parents who aren't seeking the advice they need – 42 per cent admit they still wouldn't know where to go if planning another child.
According to the government-backed service, which is funded by a levy on the financial services industry, financial planning should start before the baby is born. To help, it has launched a "Baby costs calculator", a free online tool – at moneyadviceservice.org.uk/parents – that calculates how much a first baby costs up to the age of 12 months.
Siobhan Freegard, co-founder of the Netmums website, said: "Out little bundles of joy can cost big bundles of cash. It's vital to plan and save hard before your baby arrives or you could face money worries in that precious first year."