The Turnbull government has rejected a call to delay the full rollout of the $22 billion National Disability Insurance Scheme, despite a major report finding the current timetable is compromising the quality of care and threatens the scheme's financial viability.

The Productivity Commission said the current timetable simply "will not be met" as the scheme struggles under a "tsunami" of demand. Federal and state governments must start planning now to delay the start of the full scheme beyond 2019-20, it suggested.

The commission has also warned of acute skills shortages and other price pressures that could force up the cost of the scheme, described as the biggest social reform in Australia since the introduction of Medicare.

In its final report to the government after a year-long inquiry, the commission says the NDIS - currently in a transitional phase as it ramps up towards full launch - is already improving the lives of many participants, their families and carers.