A dramatic increase in the number of young men doing jobs traditionally held by women has left them worse off than the previous generation, according to a study.

By the time they hit 30, 'millennial' men – those born between 1981 and 2000 – have earned around £12,500 less than those in 'Generation X', defined as those born between 1966 and 1980.

It makes them the first generation to earn less than their parents' generation, prompting a senior MP to warn that many young men are being 'denied their traditional role as breadwinners'.

In 1995, a 25-year-old man earned an average salary of £13,800 – worth the equivalent of £23,300 today. But the average for a 25-year-old in 2015 was £21,700.

By the time they hit 30, 'millennial' men (stock photo) – those born between 1981 and 2000 – have earned around £12,500 less than those in 'Generation X'

The pay gap has been caused by a surge in the number of young men working in bars, restaurants and shops as the manufacturing industry has declined but the services sector has boomed.

Think tank the Resolution Foundation said its analysis shows that the 'long held belief that each generation should do better than the last is under threat'.

It explained the 'stunted pay progress for young men has been exacerbated by an increase in part time work'. Since 1993, the number of men aged 22 to 35 working part time in the lowest paid occupations such as basic admin and sales, has increased fourfold.

However there are fewer young women working in these jobs.

Figures from the Office for National Statistics show that the number of young men in retail jobs has almost doubled from 85,000 in 1993 to 165,000 in 2015/16.

Although women remain significantly more likely to work in retail than men, the number of young women doing these jobs has fallen over the same period.

The number of young men working in bars and restaurants has also trebled from 45,000 to 130,000 since 1993.

Plain 'bad luck' is also one reason millennial men are worse off, with the onset of the financial crisis in the late 2000s coming just as many were graduating from university.

But while women have 'overwhelmingly transferred' into higher skilled jobs in sectors such as finance and teaching, men are 'more evenly split' between higher and lower paid occupations. This is partly because of the 'forward march of education and feminism', which has helped more young women climb the career ladder.

Generation X has been defined as people who were born between 1966 and 1980 (stock photo)

Torsten Bell, executive director at the Resolution Foundation, said: 'The long held belief that each generation should do better than the last is under threat.

'Millennials today are the first to earn less than their predecessors. While that in part reflects their misfortune to come of age in the midst of a huge financial crisis, there are wider economic forces that have seen young men in particular slide back.'

Last night Frank Field, the Labour chairman of the work and pensions committee, said the difficulties faced by younger men today have wider social consequences.

'This group of younger men are being denied their traditional role of being breadwinners – which makes them far less attractive in the marriage market,' he said. 'This means fewer young men are getting married, which means far fewer stable families.

'This has a huge knock on effect on the nurturing of children as fathers are often not around.'

But the report points out that millennials 'don't have it all bad', as they are more likely to have gone to university than any previous generation.

This means that while they are likely to earn less in their 20s at the start of their careers, their pay should be boosted in the longer term.