Holyrood's health committee has called for a public inquiry into hepatitis C infections caused by NHS treatment.
Hundreds of Scots were infected by contaminated blood products
Hundreds of people in Scotland were infected with hepatitis C from contaminated blood products before 1991 when new tests screened out the virus.
Campaigners have long demanded a public inquiry but their calls were rejected by a parliamentary vote in December.
In a narrow vote, the committee has now ruled many questions remain unanswered despite their own investigation.
The vote was decided by the committee's convener, the Scottish National Party's Roseanna Cunningham.
MSPs said they were particularly concerned about ineffective efforts to trace and warn those who might have been infected by suspect blood products.
Lawyers for the Scottish Haemophilia Forum said they had uncovered new evidence they claim shows some patients waited up to 20 years to find out they were infected.
The Scottish Executive has admitted a "look back" exercise failed to find dozens of patients treated with blood that may have been infected.
However, Health Minister Andy Kerr said that is not relevant to calls for a public inquiry.