Ian Rankin, James Robertson and Karen Campbell top a list of more than 100 writers and campaigners urging the UK government to back the release of jailed Saudi blogger Raif Badawi.
The novelists are among 128 literary figures from Scotland and around the world to sign a letter to Prime Minister David Cameron in support of Mr Badawi, a dissident who spent a year in exile in Glasgow.
Their intervention comes as the blogger, who has been on hunger strike, tomorrow prepares to mark four years behind bars in the autocratic regime, seen as an ally of the UK in the Middle East. He was sentenced to 10 years in prison and 1000 lashes for allegedly insulting the Saudi royal family on a blog.
The letter, organised by Scottish PEN, the freedom of expression campaign, has also been signed by writer and journalist Neal Ascherson, poet Christine De Luca, playwright Jo Clifford and Glasgow SNP MP Stewart McDonald, who has highlighted the Badawi cause previously championed by his Labour predecessor Tom Harris. Mr McDonald has described Mr Badawi's punishment as "a slow death sentence".
Its authors said: "Charged with insulting Islam through electronic channels and brought to court on several charges including apostasy, Raif has become a symbol of both the threat to free expression and the extent to which Saudi Arabia attacks those brave enough to speak out.
"On this anniversary we come together to say that this cannot stand, his imprisonment and brutal punishment represents the limits of our commitment to free expression.
"We call on the UK government to do more to secure Raif’s release. Any reluctance or resistance on our part undermines our commitment to fundamental freedoms that should form the foundation to any and all of our relationships with key partners across the globe."
The writers – the letter is also signed by figures from the Balkans, the Nordics, England, Wales and Ireland, the US, the Philippines, South Africa and Canada – believe the British Government could do more to pressurise their allies.
Mr Badawi spent a year in Glasgow in 2007 after he felt Saudi Arabia after he was first arrested because of things he had published on his website. He returned to the country in 2012 but was arrested and convicted.
The Scottish Government has expressed its support for the liberal secularist and the UK Government has condemned his sentence while stressing it cannot interfere in the judicial system of another country.
Mr Rankin, Mr Robertson, Ms Campbell and the other writers, however, called on Mr Cameron to call for Mr Badawi's immediate release and strike a blow for freedom of expression.
They said: "Freedom of expression is a barometer of the health of the society; Saudi Arabia’s treatment of Raif and the countless others is a stark indictment of the commonplace repression that challenges any commitment to civil liberties that Saudi Arabia may profess to have.
"Commitments are not enough; they need to be represented by positive action.
Four years is too long a time to spend in prison, a day is too long when the crime amounts to free expression, but we must ensure that this anniversary is the last Raif Badawi spends behind bars."
Earlier this year a Saudi court jailed a man for 10 years and sentenced him to 2000 lashes for tweeting about his atheism. Opposition activists in 2012, when Mr Badawi was jailed, claimed Saudi Arabia had 30,000 political prisoners. The Kingdom denies this.