SHADOW Foreign Secretary Douglas Alexander has called for a more open debate on independence after hitting out at online abuse heaped on Scots comic Susan Calman.

The Labour MP accused some Nationalists of choosing to belittle their opponents instead of engaging in a battle of ideas in the run-up to the referendum.

In an article in today's Herald, based on a lecture he will deliver tonight in memory of former Lanark MP and government minister Baroness Judith Hart, he claims attacks on Ms Calman were an example of widespread "intolerance" shown towards opponents of independence.

Ms Calman complained of bullying and death threats after she poked fun at Alex Salmond on BBC Radio 4's News Quiz. She refused to say which way she plans to vote in the referendum but was targeted partly because she is the daughter of academic Sir Kenneth Calman, whose devolution proposals were adopted by the pro-UK parties.

Mr Alexander said: "This truly appalling episode is just the latest example of the hate-filled outpouring of the so-called 'cyber-nats', whose characteristic is general intolerance to everybody and anybody who does not share their outlook.

"How has Scotland – rightly proud of our openness and tolerance – arrived at a place where a comedian is smeared, bullied and even threatened for speaking out and making light of the pretensions of politicians?"

The Paisley and Renfrewshire South MP said the tactic was also adopted by senior figures in the Yes campaign.

He said: "Just this week, we saw the SNP's Angus Robertson attempt to belittle the campaign against independence, by branding people who opposed separation as having the view that "people in Scotland are uniquely poor, stupid and incapable of governing themselves".

He said this "crass and offensive" view patronised the Scottish people "who are quite capable of making an informed choice between different viewpoints without one side denigrating the other".

An SNP spokesman said: "We agree with Douglas Alexander – denigration of people has no place in the referendum debate."