Common violations include failures to provide employees with a pay slip, paid holiday and the minimum wage, analysis from the Resolution Foundation concluded.
Employees at small businesses, which employ fewer than 25 employees, are most likely to not be given pay slips and holiday leave, the think-tank found.
Around one in 20 workers reported receiving no paid holiday entitlement, with the figure increasing to one in seven workers in the hotel and restaurant sector.
The organisation also found around one in seven in this sector do not receive a pay slip, a rate 50% higher than the rest of the labour market.
Resolution Foundation senior economic analyst Lindsay Judge said the style of contracts commonly used by hospitality businesses left them prone to violations.
She said: “The UK has a multitude of rules to govern its labour market – from maximum hours to minimum pay. But these rules can only become a reality if they are properly enforced.
“Labour market violations remain far too common, with millions of workers missing out on basic entitlements to a pay slip, holiday entitlement and the minimum wage.
The think-tank called for Government investigations into the sector as it launches its own three-year research project into the issue.
Judge added: “The Government’s welcome proposal to create a new single enforcement agency should leave it better placed to tackle these labour market violations than the multiple bodies currently operating, as long as it’s properly empowered and resourced.
“Our analysis suggests that while violations take place across the labour market, the Government should also prioritise investigations into sectors like hotels and restaurants, along with firms that make large use of atypical employment contracts, as that’s where abuse is most prevalent.”
British Beer & Pub Association chief executive Brigid Simmonds said the pub sector took the treatment of its employees seriously.
She said: “Employees and their skills are greatly valued by our sector – without them, we wouldn’t have our world-class beer and pubs.
“The welfare and work-life balance of employees is also of the utmost importance to our members, who equally take compliance with workplace regulations extremely seriously.
“It is important that pubs and the wider hospitality industry ensure all legally required workplace entitlements are given to staff.”