False invoices, organised crime syndicates and overcharging for services are behind exploitation of the scheme, NDIS Minister Bill Shorten says.

"These crooks leave patterns ... we just need to give the resources to our regulators to catch the crooks, detect the patterns and stop the operations," he told reporters in Melbourne on Monday.

"The NDIS is a generous scheme ... but it is beyond belief, it is beyond anger, that you have criminals and other opportunists who are simply robbing the poorest, least well-off people in Australia and getting rich on it."

Mr Shorten's comments come after Australian Criminal Intelligence Commission head Michael Phelan told the Nine Network as much as 15 to 20 per cent of the $30 billion-a-year scheme could be being misused.

Yet the minister insists the figure is in the "tens of millions" and not anywhere near the estimate Mr Phelan described.

Mr Shorten said negligence by the former government contributed to fraud within the scheme.

"(The coalition) made the life of people who were receiving packages difficult but they seem to give a pass to the people who are robbing the scheme and overcharging," he said.

"The fraud squads, the investigation teams in the NDIS, were underfunded ... I don't think there was enough cooperation between the National Disability Insurance Agency and other parts of government."

Mr Shorten addressed the national disability summit on Monday and will meet with the agency in charge of running the scheme.

Australian Associated Press