Mr Fischer used Tuesday's 50th anniversary of the first intake of conscripts on June 30, 1965, to call for those responsible to "come clean".

"Somebody in Canberra played god [with peoples lives]," he said.

"They are now retired former senior members of the Department of Labour and National Service.

"In the interests of historical accuracy and fairness they should now step out and explain the methodologies they used."

Mr Fischer's concern is there appear to have been serious inconsistencies in the way in which the draft was run which meant men born on some days had a much greater chance of being called up than men born on other dates.

The inconsistencies included the failure to adjust the numbers required to take into account the leap years between 1965 and 1972, fiddles to achieve a "geographic balance" at the expense of statistical impartiality and the practice of rounding up and rounding down results for the last day of each six-month conscription period depending on whether more or less men were required to fill the quota.

"There are some very curious examples," he said. "Only four marbles came up for men born on January 1, 1946, compared to 13 marbles for men born on June 30, 1946. This is almost beyond the standard deviation [you would expect]."

A man born on June 30 that year was more than three times as likely to be conscripted as a man born on January 1.

Mr Fischer was the first Vietnam-era "nasho" to be elected to parliamentary office when he won the NSW Legislative Assembly seat of Sturt for the NSW Country Party on February 13, 1971, after returning from the war.

He served as a 2nd Lieutenant with 1 RAR from July 1, 1966, to March 31, 1969, after graduating from the high intensity Scheyville officer training course, and has no personal regrets. "I was happy enough to serve," he said.

Mr Fischer was elected to the Federal Parliament in 1984, was a former trade minister, and served as John Howard's deputy prime minister from 1996 to 1999.

Mark Dapin, in his book The Nasho's War, said the Menzies Government's national service scheme differed from anything Australia had ever seen before and targeted the "best and brightest" to raise the overall standard of the army's recruit intake.

"It's initial aim was to quickly raise the strength of the army from 22,500 to 37,500 troops, by calling up 4,200 youths in the last half of 1965 and and 6,900 [later raised to 8,400] every subsequent year," he said.

"Recruits would first be chosen by ballot, before further selection through medical examination, intelligence testing and security vetting. The men who passed faced a commitment of five years service, two of them full-time and and three in a reserve capacity."

The reserve training requirement was never activated.

In an unusual twist men who volunteered for the Citizens Military Forces (the equivalent of the Army Reserve) were exempt from being sent to Vietnam.

"This meant the CMF evolved from being an organisation for the citizens who were most interested in joining the military into a larger body including those who were least enthusiastic about the idea," Mr Dapin said.

Canberra marked the first intake of national service with a march and a ceremony at the Australian War Memorial attended by the Governor General Sir Peter Cosgrove AK MC (Retd) on Tuesday.