Parents are finding themselves "hyperinvesting" time and money in the lives of adult children. The young adults concerned may not see any problem, even though living at home for too long can damage social confidence and independence and induce conflict, stress and dependency.

The new glossary has been spawned by the fact that the road to independent adulthood today is a much longer and rockier one than it used to be.

Money worries, clashes of lifestyles and young adults treating the family home "like a hotel" all help to pile on the pressure for parents when they find themselves living with their grown-up sons and daughters for much longer than they'd ever expected. The family home can become a battleground, with parents no longer understanding what their role is – or when they will ever have any privacy.

In some serious cases, parents are dealing with physical and verbal aggression, alcohol and drug-taking at a time when they thought they would have happily moved on to the next, child-free phase of their lives.

The charity Parentline Plus is so concerned about the number of calls it's receiving from distressed parents that it is drawing up a self-help guide for parents, and dedicating a new area of its website to problems specific to parents with adult children living at home.

One caller told the charity's free 24-hour helpline: "I'm not sure what my role is with my son now. As a mother I feel very insecure... (it's) difficult for me as a parent to adjust to this new relationship."

Another parent complained that the house had become beset with constant arguments about alcohol abuse, bad language and "lack of respect for us and our home by our son". Many parents said they found it difficult to persuade their children to look for work.

Student debt, job instability, the shortage of affordable housing and the lengthening of adolescence – itself a by-product of longer life expectancy – mean adult children are more likely not to leave home until their late 20s, or leave and return whenever accommodation, money or relationship problems arise.

The proportion of men in their 20s living in the parental home has grown from 59 per cent to 80 per cent in the last 15 years, according to Government figures. Among women, the figure has risen from 41 per cent to 50 per cent.

Back in 1970, an average 21-year-old would already be married or about to marry, or already be caring for a newborn child of their own. The average age of first marriage is now 30 in men and 28 for women.

A survey of 575 calls to Parentline Plus's helpline showed that 10 per cent concerned problems with adults still living at home. Nearly 70 per cent worried about regular use of Category C drugs. Children who had gone away to college or university and tasted freedom before returning were felt to be more likely to treat the parental home like a (free) hotel.

One parent said: "My 20-year-old son is living at home, working full-time and reluctant to leave. I find that I am ready for him to move on, as he is not a very considerate housemate and I feel he would benefit from the experience. I am wanting to move in with my partner without my son coming, too."

The charity's report Will They Ever Fly The Nest? says there is a supposition that once children become adults they "magically become trouble-free and responsible".

The report calls for the Government to give more information and support to parents of young adults living at home, in order to influence work and personal choices. They should be able to access help on a host of issues, from housing benefits to training opportunities, says Dorit Braun, chief executive of Parentline Plus.

"Living with young adults is as perplexing and concerning as any other stage in a parent's journey, yet parenting strategies seem to end with adulthood, as though once children become adults parents are 'off the hook'," says Ms Braun.

"Parents want to offer informed advice to their adult children about what opportunities are open to them and they want as much support for this part of their parenting role as they have done throughout their family journey."

The charity also conducted research with parents which revealed that the clash of different lifestyles between the two generations was the greatest bone of contention. Despite some clashes, the majority of parents thought their children enjoyed still living at home, but felt the family got along better when the children were working.



www.parentlineplus.org.uk Helpline: 0808 800 2222