The University of Strathclyde, where CBI Scotland director Iain McMillan sits on the advisory board, has joined Skills Development Scotland (SDS) and the Law Society of Scotland as the latest organisations to resign after the CBI formally registered as a supporter of Better Together.
Glasgow, Aberdeen and Edinburgh universities resigned yesterday, while Aberdeen's Robert Gordon University also expressed its disapproval at the decision but chose to remain a member.
Dundee University and Caledonian University are also said to be reviewing their memberships this week.
Scottish Enterprise, VisitScotland, STV, the Balhousie Care Group and energy company Aquamarine Power all resigned from the CBI in recent days.
A University of Strathclyde spokeswoman said: "The University of Strathclyde has reviewed its membership of CBI Scotland and has taken the decision to withdraw from the organisation."
A SDS spokeswoman said: "In light of the CBI's decision to register as a campaign organisation for a No vote in the referendum, SDS has no option but to resign as a member."
Law Society of Scotland chief executive Lorna Jack said: "Over the last three years, the Law Society has been an active but firmly non-partisan participant in the debate on Scotland's future. We've asked difficult questions and raised issues that need addressed by both sides of the referendum campaign in order to better inform our members and the wider public.
"We do not believe we could credibly retain our impartiality whilst being a member of and actively contributing to another organisation which is formally registered with the Electoral Commission to campaign for a No vote. That is why we have resigned from the CBI today."
CBI director general John Cridland defended the decision to back Better Together yesterday, insisting it was made "for compliance reasons" and did not represent any wish to campaign to influence voters' opinions.
It emerged on Friday that CBI Scotland had registered with the Electoral Commission, meaning it can spend more than £10,000 on campaigning during the referendum period.
Registering as a campaigner also gives access to the electoral register and the right for representatives to attend postal vote opening sessions, polling stations and the counting of votes.
Glasgow Caledonian University later confirmed that it is to withdraw from membership of CBI Scotland.
A spokeswoman said: "The CBI's decision to register with the Electoral Commission on the issue of Scottish independence is incompatible with the university's neutrality. GCU will, however, continue to provide a forum for open debate on the independence referendum."
Highlands and Islands Enterprise, which performs a similar public function to Scottish Enterprise in the north, has also resigned from the CBI.
A spokeswoman said: "In light of CBI Scotland's recent decision to register with the Electoral Commission, it is inappropriate for Highlands and Islands Enterprise, given our impartial political position, to remain in membership and we have therefore resigned."