School leavers have a new and powerful source of career advice — with the Prime Minister urging them to ditch their plans for law unless they actually want a job as a lawyer.

"I think too many kids do law," Malcolm Turnbull said this morning.

The PM revealed he actively discouraged students from heading for a university law course unless a legal career was their dream.

"They could spend those years at university doing something more useful and more valuable to whatever career they ultimately took on."

The PM suggested budding university students looking for a general qualification should consider picking a different option.

"A lot of kids do law as though it is a sort of interesting background qualification and it is not," Mr Turnbull told Canberra radio 2CC.

"If you want to have a general humanities degree that is an intellectual endowment that isn't particularly specific in a vocational sense then you would be better off doing languages, history, literature, philosophy. Frankly you would be better off doing economics."

Mr Turnbull speaks as a law graduate.

He famously acted for former British intelligence officer Peter Wright when Margaret Thatcher's government was trying to ban publication of the Spycatcher memoir.

"I did law because I wanted to be a lawyer and I practised as a lawyer for a decade," Mr Turnbull said.

His advice was aimed at those who did not have a goal to be a solicitor or barrister.

"Why would you do dentistry if you don't want to be a dentist, or medicine if you don't want to be a doctor?" Mr Turnbull said.

In 2015, Graduate Careers Australia figures showed a quarter of law graduates who wanted a full-time job could not find one within four months of graduating.

The number of students choosing law degrees has increased since the cap on admissions was removed.