This was the result of new evidence showing lack of resources was the reason for limited efforts to track down patients infected with the fatal virus, the Health Committee narrowly voted for an inquiry by just one casting vote from convener Roseanna Cunningham.
Margaret Curran, the minister for parliamentary business, said the vote was "inconsistent" with usual parliamentary procedures.
Campaign claims that up to 3,500 people were infected with hepatitis C during the 1970s and 1980s and they therefore have been calling for a public inquiry for many years.
A letter from the Scottish National Blood Transfusion Service to the Scottish Office stating a number of infected patients will not be tracked down without additional resources was what they produced now and it has string implications..
However, ministers have claimed everything was done to track down infected patients.