A Senate committee has heard some mining and infrastructure projects are delayed or cancelled because of a lack of skilled staff.

Stephen Durkin from Engineers Australia says the skills shortage is getting worse each year.

"The statistics are that there is about 9,500 engineering graduates each year coming out of Australian universities and TAFE," Mr Durkin said.

"But the annual demand for engineers ranges from between 13,000 and 20,000 engineers per annum and that's been the trend for the past several years."

Mr Durkin has urged the Federal Government to immediately implement the committee's recommendations.

The committee also heard many qualified engineers were currently out of work.

Committee chairman Liberal Senator Chris Back says the Government should encourage former engineers to return to the workforce.

"Fifty per cent of engineers are no longer practising actively, including senior engineers and older, semi-retired engineers," Mr Back said.

"I would have thought with changes to workplace practices they probably, in many instances, are the ones that the big projects and the big project managers are probably screaming out to get back in."

The committee has also been warned the mining boom and major infrastructure projects could be stifled if more people do not study engineering.

Mr Back says high school children should be encouraged to study mathematics and science.

He also says the public service should train more engineers and women should be encouraged to take up the occupation.

"I reckon there's tremendous opportunity to be able to improve that," he said.