Company sick pay is not available to 34% of working Britons, amounting to 11m people, research by LV= has revealed.
Of the 11m, 8m are employed by a company but would only receive statutory sick pay if they fell ill, £88.45 per week, over £300 less than the average UK weekly pay of £409.
Among those who would only receive statutory sick pay 15% (1.2m) are on zero-hours contracts while 10% have not worked long enough to qualify for their company sick pay scheme.
Temporary and short-term workers similarly would not receive company sick pay, accounting for 23% of the 8m who would not receive it.
The 9% of the UK workforce who are self-employed would not receive any pay if they were ill.
Employees working for SMEs are also potentially vulnerable LV= warned, since they tend to have less generous sick pay packages, with 36% of employees in their twenties working for them.
This compares to 18% of over 50s working for SMEs, highlighting the greater potential vulnerability.
Myles Rix, managing director of protection at LV= said: "The UK economy is changing, with zero-hours contracts, freelancing, contract work, and self-employment all becoming more common.
"As a result, fewer workers now qualify for company sick pay, meaning they could struggle to meet their financial commitments if suddenly unable to earn a salary due to accident or illness.
"A contingency plan such as income protection offers workers peace of mind so they can focus on recovering without worrying about whether they can pay their bills."
