National Disability Services Tasmanian state manager Will Kestin said the cap itself was not the issue but the government's premise that NDIS participants in the state would have their transport needs covered was "not the case".

He said the reduction of the cap from $1000 to $350 next year would put a large number of those reliant on the subsidy at risk of isolation.

The government has justified the cap, which provides a 60 per cent discount of up to $30 per trip, as only 25 per cent of people accrue more than $350.

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Mr Kestin said a cap of $700 in the second and third year would cover "all but two or three" people, adding that the NDIS was "never supposed to replace the taxi subsidy ... state government's still have a responsibility".

Speaking in Launceston on Thursday, deputy Labor leader Michelle O'Byrne called on the government to reverse the cap which would affect about 1400 people.

Disability advocate Jane Wardlaw also called for a reversal and said the cap was "discriminatory against our most vulnerable people".

Transport Minister Michael Ferguson said he was only new in the portfolio and would look at all supports the state offered and accused Labor of "playing politics".

He said the government had fulfilled "100 per cent of our cashing-out obligations" to support the funding of the NDIS but wanted to provide further temporary support for those who were not receiving transport in their packages of care.

"We've continued our scheme of support so that we can provide a taxi subsidy payment for people who need a bit more support while the NDIS is in its early days," Mr Ferguson said.

On Wednesday, federal Labor NDIS spokesman Bill Shorten weighed in on the issue, saying he was "appalled" that some Tasmanians could be "priced out of the market".

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