Church leaders have expressed "very grave concerns" about proposals to assisted suicide legal in Scotland. 

Rev Andrew Downie, Moderator of the United Free Church of Scotland, and Rev Bob Akroyd, Moderator of the Free Church of Scotland, are urging MSPs not to support Liam McArthur's Bill to legalise assisted suicide. 

In a letter to all 129 MSPs, they say that supporting the proposed legislation would cross "a bright red moral line" and "mean that Scottish society has lost its trust in the inherent value of all human life".

They warned that Scotland risks "becoming an ethical wilderness" and said that the Scottish Parliament "must always maintain that all lives are equally meaningful".

Legalising assisted suicide would send the message that some people "have become unworthy of life", they added.

"We believe, as indicated in the book of Genesis in the Bible, that everyone is created by God in his image – an image that reflects and expresses his equal love for everyone. As a result, every life has equal value – a value which can only be measured by the sufferings of Jesus Christ on the cross for humanity," the church leaders write.

"We also believe that for a civilised society to survive, everyone should believe that everyone else is equally valuable. It is very important, therefore, to understand the consequences for the Scottish Parliament if it crosses the bright red moral line of acknowledging that, if a life does not reach a certain quality, then it loses its worth and can be ended.

"It would become a society where the value of all human life is actually unequal and purely relative. It would be a society where the worth of every human life could then be graded depending on its usefulness, meaningfulness, and the amount of pleasure it may experience."

The letter ends with a call for quality palliative and hospice care to be developed across Scotland to make people "as comfortable as possible without intentionally ending their lives".

"Society will then continue to recognise these patients as having full worth and value while accepting them, unconditionally, for who they are in compassion and care," they said.