Opposition Leader Luke Foley's comment that he will not back voluntary assisted dying laws because he opposes "the state sanctioning the taking of human life" has been branded "offensive" by the husband of a terminally ill woman advocating for the change.

A private members bill was introduced to the NSW upper house last Thursday, which would see terminally ill NSW residents aged 25 or over legally able to end their own life with medical assistance.

Labor and Coalition MPs will be granted a conscience vote on the bill due to be debated by the end of the year.

Its introduction prompted Mr Foley to tweet: "Personally, I will vote against. I oppose the state sanctioning the taking of human life. Opposed to capital punishment & euthanasia".