Some 17 per cent of over-55s who are providing financial help to loved ones will be, or already are, worse off as a result, Legal & General and the Centre for Economics and Business Research (CEBR) found.
One in ten also said they felt less financially secure and 4 per cent had postponed retirement after supporting family or friends onto the housing ladder, according to the research.
Women were found to be more likely than men to have accepted a lower standard of living after providing financial support.
People approaching retirement aged 55 to 64 were also particularly likely to be feeling the strain – with money being siphoned from places such as pension pots, downsizing to smaller homes and equity release to help younger generations.
Legal & General calculates that, based on the average contribution by the “bank of mum and dad”, an over-55 household can expect to be £18,000 worse off on average after providing financial support.
The research also found that “bank of mum and dad” lenders were unlikely to take advice in regard to the impact their giving may have on their own financial future.
Before gifting money to help family or friends onto the housing ladder, more than three-quarters (77 per cent) did not speak to a professional adviser or even seek information online.
Chris Knight, chief executive officer, Legal & General retail retirement, said: “Parents and grandparents across the UK are often digging deep into their pension pots to support loved ones, balancing the housing needs of their children and grandchildren with their own retirement goals.
“Worryingly, in the majority of cases, these individuals aren’t taking advice before they ‘lend’.”
He said the financial services sector should re-think how it communicates with people and continued: “It means getting people thinking about retirement income earlier, helping them build their retirement plan and laying out all the options available to them.
“If we can do this, we can help people to be this generous without leaving themselves short – helping their family onto the property ladder, but also ensuring they have the best retirement they can.”