The Disability Rights Commissioner has clashed with MPs over a proposed euthanasia law, claiming it could apply to people with intellectual disabilities.

Photo: Supplied.

Paula Tesoriero published a scathing assessment of David Seymour's End of Life Choice Bill earlier this year and did not ease off during the first public submissions in a parliamentary select committee on Monday.

"This choice - under this legislation - sends a message to society that the lives of disabled people are not worth living."

The scope of the legislation was ambiguous and far too broad, she said.

"This bill intends to go beyond terminal illness. What is unclear is exactly what conditions are in or out. Does Parliament intend that conditions like muscular dystrophy, multiple sclerosis, a declining mental health condition be included?"

Labour MP Greg O'Connor pushed back against the argument and said people with intellectual disabilities were not eligible.

"I have an intellectually disabled son, so I've been very careful to look at this," he said.

But Ms Tesoriero disagreed and said it was "entirely feasible" people with multiple disabilities - one of which was intellectual - could be affected.

The proposed law gives people older than 18 and suffering from a terminal or debilitating illness the option of assisted dying.

To be eligible, the bill states a person must be in an "advanced state of irreversible decline" and able to understand the consequences of their decision. Two doctors and, if required, a psychologist would be required to confirm a person's eligibility.

The bill's sponsor ACT leader David Seymour said he was deeply disappointed that Ms Tesoriero was "spreading misinformation" as intellectually disabled people did not qualify under the bill.

"It's very ironic that the Disabilities Commissioner of all people would be saying that a person who's perfectly capable of making a decision ... should have fewer rights and choices than other people."

Photo: RNZ

Ms Tesoriero told the select committee many disabled people could not freely exercise their choice in New Zealand.

"We live in a world where people focus on fixing us, not on removing the barriers that make us disabled.

"In the absence of adequate services, we run the risk that choice under this bill becomes a Clayton's choice for disabled people."

A "Clayton's choice" is a choice that exists in name only and isn't genuine.

But Mr O'Connor said many disabled people were perfectly able to give well-informed consent.

"You have to be careful - because it's almost like you're saying, 'Leave disabled people over here, because they're not capable of the same ... mental capability'."

More than 35,000 written submissions have been received on the bill - thought to be a record high. At least 3500 people are expected to address the select committee.