According to Direct Line Business Insurance, on top of the 6% of Brits who have found a second job, a further 1.5 million (4%) have launched their own own business.
Over half take on extra work in the evenings.
The trend in people looking to boost their income goes beyond conventional self-employment or second jobs, the study found.
More than a third (36%) have undertaken additional activities in the past six months to increase their earnings, with 11.5 million (24%) people making extra money online, potentially selling merchandise through online auction sites or taking on freelance design work.
Approximately 800,000 people have launched businesses in their local area to earn extra income.
On average, Brits who have taken on additional work to boost their bank balance are pocketing almost £2,536 a year. Over two million people are clocking up at least 18 hours a week, through second jobs or extra work.
Jazz Gakhal, head of Direct Line Home Business Insurance, said: "Many people are exploring creative avenues to make extra money. People are looking to supplement their monthly income be it selling online, freelancing, or starting their own business.
"Some will be building up their own companies at home while maintaining the security of a regular income before making the switch to being a full time business owner and manager."
However, people are being warned that they may not be covered by their existing insurance policy if they are earning money from home to top up their monthly income.
Gakhal added: "Many people may not realise if they are completing additional work from home, they may need specialist home business insurance because they may not be covered by their home policy. If a business is based at home, it does not mean it won't have some of the potential risks a conventional business has.
"There are many things that need to be covered to ensure in the event of something going wrong, whether covering stock, protection against claims from others, or even ensuring if trading is interrupted you still have an income, home business insurance is essential."
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