The South Australian government has stepped in to ensure almost 100 home builders duped by a construction company operating without insurance have their homes completed.

GNC Homes is alleged to have signed contracts with up to 200 clients, mostly investors from Western Australia and Victoria, without the mandatory building indemnity insurance, Business Services Minister Gail Gago says.

Ms Gago says ninety-eight partially-built homes will now be finished by another company and GNC Homes may face charges over allegedly forging insurance certificates.