Catering staff could be among those affected

Unison, the local government union, claims janitors, cleaners and catering workers face being transferred to private companies if the scheme is approved.

The PPP plan will cost £74m to put into practice.

It would see two new secondary schools built in Dunoon and Helensburgh and a further 26 upgraded.

Unison officials said they are concerned that there has not been an in-house bid for school services and believe it could have a knock on effect for jobs and the local economy.

However, Argyll and Bute Council has accused the union of a deliberate attempt to throw a spanner in the works at a late stage in negotiations.

Nearby Inverclyde Council recently ditched PPP proposals which would have meant £100m worth of investment in schools refurbishment.

A row broke out when the new Liberal Democrat authority decided it was too expensive to go ahead.