Police took action against one-in-ten 18-year-old males in the year to July 2011, according to figures released by the Australian Bureau of Statistics yesterday, making them the single biggest problem group for law enforcement authorities.

And the proportion of 18-year olds committing a crime is increasing slightly each year.

Most became caught up in public order offences such as offensive language and public drunkenness as they hit legal age and began drinking more and spending more time out after dark, juvenile crime expert from the University of Sydney's Institute of Criminology, Garner Clancey, said.

''They're out and about much more than any other time in their lives, they're on public transport and in licensed venues and they're often in groups so they're more likely to be drawn into the police's net,'' he said.

NSW police have become particularly focused on alcohol-related crime, he said, with Friday and Saturday night crackdowns on everything from public urination to assault.

Public order offences were the most common crime committed by 18-year olds, followed by theft, drug offences and acts intended to cause injury.

Not only are they drinking more, teenage males are more prone to take risks as their brains are still developing, Father Chris Riley from Youth off the Streets said. However, he believes rising youth unemployment and a lack of services are behind the alarming statistics.

He said too many pockets of Sydney and country NSW remain devoid of infrastructure and services to stop teens falling into crime.

When Youth off the Streets set up services in Macquarie Fields, including a $7.3 million drop-in centre, the crime rate fell by 40 per cent, he said.

''Kids who don't have jobs, who don't have stable homes or have dropped out of school feel they can't contribute so they don't,'' he said.

''But kids have given up because we have given up on them. We want to put them down and lock them up rather than engage them.''

Glenn Broome, 48, who was incarcerated for armed robbery when he was 18, said family breakdown was leaving more teenagers without role models. One-third of marriages in Australia end in divorce.