Delegates attending the first day of the Scottish Lib Dem spring conference said the provision of the Justice and Security Bill goes against their core values. The vote comes a week after the plan was condemned by the UK party conference in Brighton.
Just one Scottish party member spoke to defend the measure, which will let judges rule that, in cases of national security, evidence may be given in private so the security services can submit their own counter-claims.
Leading calls against the legislation, party activist Caron Lindsay said justice must be seen to be done in an open court.
“I never thought I’d see the day when this fundamental basis of fairness is interfered with,” she told the conference. “Far less that Liberal Democrat MPs would support it.
“There should be no trial at all, if it is not going to be fair..
“This legislation should never have seen the light of day, and certainly never with the Liberal Democrats’ name on it.”
The vote calls for the party to commit to repealing the act in its next general election manifesto.