Media playback is unsupported on your device Media caption Welsh government ministers want to increase the number of donors for transplant by a quarter

Wales could become the only UK country with an opt-out organ donation system if politicians vote to change the law.

The Welsh government wants to introduce a system where individuals will be presumed to have consented for their organs to be donated after death unless they have specifically objected.

But opponents want families to be able to stop a donation if their relative did not express an opinion either way.

Ministers want to increase the number of donors for transplant by a quarter.

There has been opposition to the changes from Christian churches and from within the Muslim and Jewish communities.

It would mean a change from the current opt-in system, where would-be donors have to sign a register.

Media playback is unsupported on your device Media caption Martyn Griffiths: "There are days when I get fed up and don't want to go to dialysis"

A statement from faith leaders and health professionals - signed by the Archbishop of Wales Dr Barry Morgan and others - calls for a so-called "soft opt-out scheme" in the Human Transplantation Bill.

They say it would give deceased patients' families a say on donation if their relative had neither opted in or out.

A joint statement says that failure to make changes to the bill would be "inhuman, unfeeling before the suffering of relatives, and a danger to the public trust and support which are necessary for the practice of organ donation to flourish".

Analysis Even if assembly members vote in favour it will be two years before any changes come into force, while a big public awareness campaign takes place. A total of 226 people are currently waiting for organ transplants in Wales. And three patients a month die while waiting. The Welsh government says the goal is simply to save lives. Opponents insist the changes could undermine trust and add to the distress of bereaved families.

If passed by assembly members on Tuesday, the presumed consent system could come into force by 2015.

The Welsh government hopes legislation will lead to a rise in the numbers of donors.

As currently happens, organs could go to recipients anywhere in the UK, not just in Wales, although evidence from other countries with an opt-out system indicates that the rise is small with around 15 additional donors provided each year and approximately 45 extra organs.

According to the NHS Blood and Transplant service, fewer than 5,000 people die every year in the UK in circumstances that would allow them to donate successfully.

Added to that, when compatibility, organ suitability, location, time scales and consent are taken into account it means that not everyone who wants to donate actually does.

It is estimated there are around 250 people on a waiting list for a transplant at any one time - 33 people in Wales died in 2012/13 whilst waiting.

Health Minister Mark Drakeford told BBC Wales: "The legislation makes it absolutely clear that if you are uncomfortable with being an organ donor you have an absolute right in the simplest way possible to opt out of the system.

Publicise the system

"You put your name on the organ donor register saying you don't want to be a donor and that is the end of the matter.

"There is nothing to be scared of in this legislation."

The presumed consent law would apply to over-18s who die in Wales if they have lived in Wales for more than 12 months.

Media playback is unsupported on your device Media caption Emma Harrison's five-year-old son Oliver needs a heart transplant

People will be able to sign up to the organ donor register so their wishes will be known if they die outside Wales.

ORGAN DONATION FIGURES The aim of the Bill is to increase the number of organs available from Wales, potentially by 25%

On latest figures this would see the number of donors rise from around 65 donors to 80.

The average number of transplants anticipated from 15 additional donors would be approximately 26 kidneys, 10 livers, two hearts and four lungs

Just over 30% of organs donated in Wales are transplanted into people living in Wales • Q&A: Presumed consent proposals

If the law is changed, ministers will have a duty to publicise the system and almost £8m will be spent over 10 years.

The bill would involve transferring some powers from the UK government to Welsh ministers.

The Kidney Wales Foundation (KWF) has campaigned for a law change on organ donation and described the bill as "progressive law".

Roy Thomas, KWF chief executive, said: "The Welsh government has seen this bill scrutinised properly and several detailed consultations have been undertaken with the Welsh public.

"This law is further progress and evidence shows it will increase donation rates."

Meanwhile, in Northern Ireland a public consultation is under way about adopting an opt-out system. In Scotland, ministers have said the option was "not completely off the agenda" but they have argued that progress has been made under the current system.

The Department of Health said a taskforce had recommended against moving to an opt-out system for England in 2008.

A spokesman added: "We are working closely with the Welsh government to ensure their policy does not negatively impact on our work to promote voluntary organ donations."