He said a number of polls had shown that up to 75 per cent of Kiwis were in favour of legalising euthanasia, with appropriate safeguards.
"MPs will have received many emails from opponents of my Bill. They now need to ask themselves how many of those emails actually came from New Zealand voters.
"We are used to the silent majority being drowned out by a vocal minority. New Zealand MPs have now found out that the minority opposed to assisted dying is so loud we can hear them from Australia."
The email from Right to Life Australia quotes Renee Joubert, executive officer of Euthanasia Free NZ, that "dirty politics" has brought forward the vote on Seymour's bill, and it is crucial that MPs receive thousands of messages in opposition today.
Labour MP Deborah Russell received hundreds of emails - "lots of spammy ones, but some genuinely thoughtful ones too" - and created an automatic reply, which explains why she will vote for the legislation to proceed to the select committee process.
In her response, Russell explains why she is undecided on whether she will vote for the legislation at its second and final reading.
"While I respect the right of autonomous fully informed adults to make decisions for themselves, I have some grave concerns about vulnerable people, including the elderly and people with disabilities."
The End of Life Choice Bill is based on an earlier piece of legislation drafted by former Labour MP Maryan Street.
It would allow mentally competent New Zealand adults who have a terminal illness likely to end their life within six months, or have a grievous and irremediable medical condition, the choice to ask a doctor to help end their life at the time of their choosing.
The Director-General of Health would establish a group of medical practitioners who would maintain a register of health professionals willing to participate in assisted dying.
A new process would require two medical practitioners to be satisfied a person meets the required criteria. The second would be independent of the patient and initial doctor.
Most parties are allowing MPs to lodge conscience votes, but NZ First's nine MPs will vote as a bloc.
The party's coalition agreement with Labour included an agreement to "allow a conscience vote for MPs on New Zealand First's Supplementary Order Paper to the End of Life Choice Bill, which provides for a referendum".
NZ First MP and party whip Clayton Mitchell told the Herald if the legislation passes its first reading tonight, his party expected that Supplementary Order Paper to be introduced either in the select committee stage, or after the second reading during the Committee of the whole House stage, where amendments can be proposed and voted on.
Mitchell said the amendment would mean that if the End of Life Choice bill passed its final reading, it would not come into effect until a majority of the public supported it in a binding referendum.
NZ First was going to vote against Seymour's bill, until Seymour today agreed to publicly support holding a referendum on the legislation.
The issue of voluntary euthanasia was thrust back into the spotlight by Lecretia Seales. The Wellington lawyer, dying of brain cancer, asked the High Court to give her the legal right for a doctor to help end her life.
On June 5 in 2015, soon after being told that her court bid was unsuccessful, Seales died of her illness, at the age of 42. A judge ruled that only Parliament could make a law change allowing that legal right.
