A new operator took over the route on Sunday amid concerns about the timetable and the type of boat being used.
Strathclyde Partnership for Transport transferred the contract from Greenock's Clyde Marine Services to Clydelink Ltd to save money.
Bosses axed the Helensburgh leg of the route because they said not enough people used it and the latest politician to raise concerns is Tory West of Scotland MSP Annabel Goldie.
She said: "What is the Scottish Government doing to ensure the retention of the Gourock-Kilcreggan-Helensburgh ferry service?
"Many people rely on this service for commuting, leisure activities and shopping excursions to Gourock.
"I can well understand local concern that the ferry service may be disrupted.
"It currently acts as a lifeline to the people who use it."
Ms Goldie's comments follow Greenock and Inverclyde MSP Duncan McNeil asking transport minister Keith Brown to confirm the new contract was awarded properly by SPT.
Transport Scotland says the service is the reponsibility of the SPT, which has said it is confident about it.