Millions of underemployed workers in Britain are blocking opportunities for people struggling to enter or to return to the labour market, a research published on 29 February has shown.

According to figures released by the Resolution Foundation thinktank, million of UK workers are either working less hours than they would like or they are stuck in the wrong job, adding that an extra 5m hours of work a week are needed to satisfy employees' demands for more work.

The report, which was published ahead of a wider-scale research from the same thinktank set to be released later this week, found that giving the opportunity to underemployed workers to work longer hours would free-up a number of part-time roles for individuals seeking to enter the labour market.

Among those, the Resolution Foundation said, are people currently defined as economically inactive – many of whom face caring responsibilities or suffer from health problems.

Official data released in January showed that wage growth in Britain slowed in the three months to November 2015, even though the national unemployment rate stood at 5.1%, its lowest level since May 2008 and marginally above the 5% rate that defines full employment.

The Resolution Foundation said bringing the economically inactive into work is a pivotal factor in the government's quest to reach full employment, although that can only be achieved via better mobility in the jobs market and increased working hours for the underemployed.

Laura Gardiner, a senior policy analyst at the Resolution Foundation, said the number of economically inactive people was vastly superior to that of the unemployed - those who class themselves as both looking for and available for work.

"Many people assume that moving towards full employment simply involves getting the unemployed into work," she said.

"But the biggest potential job gains stem from bringing in the much larger group of economically inactive people. To do that we need to focus on the kind of work available, particularly for the large numbers with health problems and caring responsibilities to juggle."

Gardiner added it was crucial to make sure people capitalised on the opportunity on offer in the part-time jobs market.

"Encouraging people into part-time jobs lies at the heart of boosting employment," she said.

"The good news is that the UK's flexible labour market provides plenty of part-time opportunities. The bad news is that far too many of those jobs are already taken by people who would prefer to work more hours elsewhere."

According to the latest JobsOutlook, published by the Recruitment and Employment Confederation earlier this month, 82% of the UK business surveyed revealed they would hire permanent staff between now and May.