The MSP hoping to make assisted dying legal in Scotland says he will raise the minimum age in proposed legislation from 16 to 18.

Liberal Democrat Liam McArthur said he had considered the matter “very carefully” and the change was in line with legislation in the US, Australia and New Zealand.

If the bill passed it would allow a patient to request medical assistance to end their life, but only if they had a terminal illness and had been ruled mentally fit to make the decision by two doctors.

MSPs are scheduled to vote on the broad principles of McArthur’s bill at Holyrood on 13 May.

McArthur said he had “reflected on both the evidence provided to the health committee and assisted dying legislation in place in other countries” in making his decision.

He said: “In other jurisdictions that have changed the law to allow dying people access to the choice of an assisted death , such as the US, Australia and New Zealand, 18 is the age from which terminally ill adults become eligible.

“On balance I now feel that this would be most appropriate for Scotland.”

He urged MSPs to vote in favour of the bill and help create “the most compassionate, safe and suitable law for Scotland”.

In October last year, First Minister John Swinney said he had “not come to a final view” on the issue but added that the proposed age threshold of 16 was “a very significant issue in my mind” which MSPs will have to “wrestle” with.

MPs in England and Wales voted in favour of a bill to allow assisted dying last year, by 330 votes to 275.

Like the UK parliament, Holyrood will hold a free vote on assisted dying – which means MSPs will not be instructed on how to vote by their parties.

The Scottish bill has proved divisive, and is opposed by the Catholic Church in Scotland and the Scottish Association of Mosques.

Politicians including former First Minister Humza Yousaf and Labour MSP Pam Duncan-Glancy have indicated they would vote against it.

The Church of Scotland is “partially opposed” to the legislation becoming law, but says its official position is currently under review.

Fr Gerry Maguiness, the general secretary of the bishops’ conference, told BBC Scotland News the change in age did not affect the Catholic Church’s concerns about the bill.

He said: “In terms of the practicalities, it really doesn’t make any difference whether you’re allowed to kill someone at 16, at 18 or at 80.

“Once you allow to kill, you allow to kill. I would hope MSPs would see sense, that in this legislation we are emerging on a new way of living that makes the vulnerable and elderly very much at risk.”

Fr Maguiness added that further funding for elderly care should be the focus for politicians, rather than assisted dying.

A spokesperson for the Scottish government said it was taking a neutral position on the bill at this stage, and would consider the legislation further if it passed the first vote.

Earlier this week a Holyrood committee scrutinising the legislation declined to make a recommendation on how MSPs should vote, saying it was a “matter of conscience”.

The report from Holyrood’s health committee highlighted a number of areas it said required further consideration should the bill progress to stage two.

These include the provision and quality of palliative care, how to ensure the mental capacity of patients opting for assistance to die and the possibility of healthcare professionals being able to “opt-in” to the practice.

A decade ago, a members’ bill introduced by independent MSP Margo Macdonald, and taken on by Green MSP Patrick Harvie following her death, was rejected. This followed a 2004 attempt by Liberal Democrat Jeremy Purvis to enact similar legislation.