MSP Drew Smith wants organ donation presumed consent law
An MSP is planning to bring forward legislation on presumed consent for organ donation if the Scottish government does not act.
Labour's Drew Smith said his proposals would mirror Welsh government plans to bring in the system by 2015.
The move emerged as Holyrood's petition's committee heard details of an 18,000-signature petition supporting opting-out of organ donation.
Scottish ministers have said the option was "not completely off the agenda".
But they have argued that progress has been made under the current system, where people opt in by signing up to the organ donor register, which reached a record high of more than two million names in April this year.
MSPs on the committee heard the proposals in the petition to change transplant law, brought by the Evening Times newspaper, would help save lives.
Its editor, Tony Carlin, said: "Every day in the UK, three people die - usually needlessly - because of a shortage of suitable organs for transplantation.
"In Scotland, there are around 650 people waiting for a transplant to give them a second chance of life.
"Around 20% of those waiting for a new liver will die, not because they have to, but because a liver wasn't found in time."
The Welsh government's bill to create the UK's first opt-out system would mean everyone is considered to be a willing organ donor when they die, unless they state otherwise.
It is hoped the move would increase organs available for transplant by a quarter - but ministers have warned there is no guarantee that legislation on its own would see a higher rate of organ donation.
Labour health spokeswoman Jackie Baillie told the petitions committee there was support for a "soft" opt-out presumed consent system, where families would still have to be consulted.
She added: "My colleague Drew Smith has announced his intention to take forward a members' bill, based on the bill introduced by our colleagues in the Welsh Assembly, if the government aren't prepared to legislate."
Earlier this month, Scottish Public Health Minister Michael Matheson said an organ donation committee had been set up in every NHS board in Scotland, seven organ donation specialist nurses had been appointed and high profile publicity campaigns continued to be run.
He also said opt-out was "not completely off the agenda", and there was a commitment to review the position across the UK in 2013.