Almost half of Europe's young adults are living with their parents, new data suggests – a record level of dependency that has sobering social and demographic implications for the continent.

One of the most comprehensive social surveys of 28 European countries reveals on Tuesday that the percentage of people aged 18-30 who were still living with their parents had risen to 48%, or 36.7 million people, by 2011, in tandem with levels of deprivation and unemployment that surged during five years of economic crisis.

The data from EU agency Eurofound, obtained by the Guardian, shows that few countries are immune and that the phenomenon is not exclusive to the debt-laden Mediterranean rim. The figures show large rises in the number of stay-at-home twentysomethings in countries such as Sweden, Denmark, France, Belgium and Austria. In Italy, nearly four-fifths (79%) of young adults were living with their parents.

However, Germany, the Netherlands, Ireland and the UK saw decreases in their numbers over that period – in Britain, the figure fell from 30% to 26%.

One of the report's authors, Anna Ludwinek, said: "The situation of youth has really fundamentally changed. And it looks different from the situation of their parents and grandparents.

"It's not only the world of work that has changed but society is changing, so the transitions are becoming much more unpredictable; people are not having a job for life or live in one place for life."

She said it was a myth that living with children and parents in a multi-generational household was all "happy clappy": "Really we see that multi-generational households have very low life satisfaction and a very high level of deprivation and perceived social exclusion.

"One could argue that if you are at the age of 30 and are still living with your parents and, on top of that you have your own family, it is really difficult to start an independent life."

The data underscores the predicament of "Generation Y" – who are better educated than their forebears, but condemned nonetheless to dimmer prospects than their parents' generation.

The growing phenomenon of adults stuck living in their childhood bedrooms has, moreover, raised concerns about birthrates and demographics in an ageing continent.

The trend for parental dependency, the report's authors say, cannot be solely explained by increases in the number of people studying later into their life, as millions more 25- to 29-year-olds have also been found to be living with mum and dad.

For women aged 25-29, this figure rose by five points to 26% while the proportion for men is up three points to 34%. Even among those who have a job, the overall figure rose one point to 34%.

While young adults tend to be as trusting of institutions as their parents, faith in their national government, legal system and the press all fell among the young between 2007 and 2011.

Bobby Duffy from pollsters Ipsos Mori said he had found similar results in the UK: "Our generational analysis of attitudes in the UK has shown how much pressure the youngest generation feel under – they're the most likely to see themselves as poor even a good few years into their careers, which is historically unusual.

"This echoes the Eurofound research – it's not just those straight out of school or university who are finding it more difficult to get going with independent lives, it's people well into their 20s and 30s."

He said these results demonstrated that class and background was becoming even more of a factor in later life success.

"Those from better off or higher social class families will be much better set to deal with the pressures. The real story here isn't about generation alone; it's about how it interacts with wealth and class, leaving some younger people behind."

Peter Matjašic, president of the European Youth Forum, which represents young people across the EU, said that Europe's youth were still "in the full force of the storm" despite talk of a recovery.

He said that too many were still unemployed or, if they were in work, this was "precarious and often without the safety net of proper social security".

"This report makes worrying reading because it provides more evidence that, at the time that young people should be becoming autonomous adults making their own way in the world, they are forced to continue to live at home with their parents for much longer than before, and this is now becoming the norm in many countries where it was not common practice before."

He called on European leaders to implement concrete measures and said that young European adults should not be discriminated against on the basis in matters of social security spending.

The Eurofound report also reveals that 49% of all Europe's young adults were living in households experiencing some form of deprivation. In 2011, 27% of young adults were living in "mid level" deprivation – meaning they could not replace worn out furniture, were unable to invite friends over and could not afford to take an annual holiday.

More than a fifth (22%) were found to be experiencing "serious deprivation" and were struggling to heat their home or buy new clothes. This figure rose by six percentage points since 2007.

The rise in deprivation for young adults was worst in countries such as Greece (+15 points) Spain (+20) and the UK (+10).

Though their situation is less acute, when compared with other generations, European youth fare worst overall. "In nearly all countries young people are more likely to experience moderate levels of deprivation than the general population, but they are less likely to experience the more serious forms of deprivation," the report says. From the survey of 7,300 young adults for the European Quality of Life Survey, the report's authors point towards a growing trend of multigenerational households in which parents are increasingly having to house both their children and their grandchildren.

Correspondingly the number of working families raising a new family in their own home fell by 3 percentage points.

Family units in which three generations all live under one roof are more likely to experience serious deprivation, "suggesting that for some, such living arrangements may be involuntary and be a result of the economic crisis", says the report.

• Six people explain what it's really like living with their parents