The penalties appeared to be a coercive way of getting doctors to be involved in assisted dying, he said.
Seymour said he was willing to consider amendments to his private members bill, including to the clause which compels doctors to refer patients on.
"I think you can equally argue that it's not the most arduous thing to do for their patient," he told the Herald.
"But that's an example of something that's not set in stone. Potentially there will be changes like that."
The college of GPs said patients wanting an assisted death should have to self-refer themselves to a new register of willing doctors which will be established under the law change.
The bill requires two doctors to approve a patient's request for assisted dying, and the second doctor will be randomly selected.
Another group representing doctors, the NZ Medical Association (NZMA), said this proposed safeguard was flawed.
Appearing before the Justice Committee in Auckland yesterday, chairwoman Kate Baddock said the pool of doctors willing to take part in euthanasia was small. This would inevitably lead to patients shopping around for a willing doctor, Baddock said.
The NZMA was opposed to the law change because euthanasia could not be reconciled with doctors' ethical principles. It also said many of the legal protections were flawed.
Seymour said the NZMA did not speak for all doctors, because its membership only equated to about 20 per cent of the 14,000 practising doctors in New Zealand.
The Royal NZ College of GPs, which represents 4800 doctors, said it did not endorse euthanasia but that it was up to individual doctors to make their own decisions within the limits of the law.
However, the college wanted further changes to the legislation. The changes included raising the minimum age from 18 to 25, narrowing the eligibility criteria, and making it explicit that people could not use mental health conditions as grounds for assisted dying.
As it stands, the law change applies to people with a terminal illness, a prognosis of six months to live, or a "grievous and irremediable condition", and requires that they be in an "advanced stage of irreversible decline".
It passed its first hurdle comfortably by 76 votes to 44, but many of the MPs who supported it said their vote was not guaranteed beyond the select committee stage.
End of Life Choice Bill
• Passed first reading 76 votes to 44
• Public hearings now underway, with record 35,000 submissions to be considered
• Justice Committee expected to report back in March