Proposals to legalise assisted suicide are "unnecessary, unethical and uncontrollable", say campaigners opposed to the move.

Care Not Killing (CNK) has launched an online petition calling on MSPs to reject a Bill that would allow those with terminal or life-shortening illnesses to obtain help in ending their suffering.

The Assisted Suicide Bill is being taken forward by Green MSP Patrick Harvie on behalf of former independent MSP Margo MacDonald, who died in April following a long battle with Parkinson's disease.

It is the second attempt to pass such a Bill at the Scottish Parliament, the first having been voted down by MSPs in 2010.

Holyrood's Justice Committee is due to take evidence on the practical application and legal aspects of the Bill next Tuesday.

CNK, an umbrella group that includes disability and human rights groups, healthcare providers and faith-based bodies, says the current law making assisted suicide illegal is "clear and right" and more must be done instead to improve palliative care.

Spokesman Dr Gordon Macdonald said: "Any change in the law would place pressure on vulnerable people to end their lives for fear of being a financial, emotional or care burden upon others.

"The Scottish Parliament rightly rejected the legalisation of assisted suicide and euthanasia just four years ago out of concern for public safety."

Dr Macdonald claimed current laws are "working well", with only 150 British people having travelled abroad to commit assisted suicide or euthanasia in 10 years.

He said: "In every free democratic society there are limits placed on human freedom in order to protect the common good and vulnerable people. The law must not be changed to accommodate the wishes of a small number of desperate and determined people at the expense of the rights of others.

"Once any so-called 'right to die' is established we will see incremental extension with activists applying pressure to expand the categories of people who qualify for it. The right to die will become a duty to die."