The number of people regularly working nights has increased by 260,000 in the past five years, according to new analysis.Britain's late-night workforce has almost reached 3.2 million after a 9% rise, said the TUC.
One in eight people now work nights, rising to one in six for black workers. Three out of five night workers are male, the study found.
The North West and Yorkshire have the highest rates of night working, with one in nine workers on night duty. Night working is most common in sectors such as security, logistics, manufacturing and healthcare.
TUC general secretary Frances O'Grady said: "As the clocks change, most of us can look forward to an extra hour in bed, but while we sleep, Britain's late-night workforce will be busy.
"Whether it's firefighters keeping watch, or drivers delivering packages across the country, we all depend on the UK's army of night workers.
"Night work can play havoc with family and social life, and have long-term health impacts. Many of the jobs are tough and often solitary.
"That's why night workers deserve strong rights and protections at work, to make sure they can get on with the job safely and happily."