Nearly half of families with dependent children could not keep up their current lifestyle for a month if the main breadwinner was unable to work, a report has found.
Some 45% of families with children aged under 18 or who have adult children who are financially dependent on their parents, would run out of cash within a month, according to the calculations.
Insurer Aviva weighed up families' outgoings against their savings. Its findings suggest more than one in five (21%) families would exhaust their savings pots within a month - while a further one in four (24%) of families have no "rainy day" savings to fall back on.
Adding these two groups together, it found that 45% in total could not support their current lifestyle for a month if their main income stopped.
Even by tightening the purse strings, cutting back to the absolute minimum spend needed to support their family, one in three families (36%) could not survive a month unsupported, according to the findings.
The research found that the average UK family has just £2,004 in savings and non-pension investments to keep them afloat compared with £2,606 in monthly outgoings on essentials such as groceries, bills and their mortgage or rent.
It found that only one in three (33%) families could sustain their current spending for longer than six months.
But parents also appeared to be over-optimistic about their ability to sustain their current lifestyle, the research found.
When asked how long they could maintain their lifestyle just by dipping into their savings and investments, parents of dependent children typically gave five months as an answer.
Many parents did admit, however, that they would struggle to cut back on their lifestyle to save money if they had a sudden income shock.
Nearly one in five (18%) feel they could not reduce their monthly spending at all. Nearly half (48%) feel they have no room to reduce their spending on utility bills and council tax, while 47% say the same about their housing costs or mortgage repayments.
Paul Brencher, managing director, individual protection at Aviva UK, said: "Struggling to stay afloat financially is the last thing families need in addition to the emotional turmoil of falling ill or experiencing a death in the family.
"No-one likes to dwell on the possibility of experiencing a period of ill health or worse, but it's important families have honest conversations about how they might cope in these circumstances.
"Family finances can be complex, so all areas - such as savings, insurance, housing and other assets - must be considered."
Nearly 1,600 parents with dependent children from across the UK took part in the survey.