Originally scheduled to open in August 2017, the Balloch education campus is being built on the site of the former St Kessog’s Primary and will accommodate a new St Kessog’s co-located with an amalgamated Jamestown and Haldane primary school, additional support needs unit and early learning and childcare centre.

A report due to go before councillors revealed that contractors discovered asbestos material under concrete foundations and hard standing following the demolition of the previous school.

West Dunbartonshire Council said it was not possible to test under the foundation until the demolition phase and earlier investigations at the site found no asbestos.

Specialist contractors have now prepared a remediation programme to remove the materials, which will add another three months to the construction programme and cost £900,000.

Councillors will be asked to approve the allocation of additional funding on Wednesday, 29 June.

The local authority’s strategic director for regeneration, environment & growth, Richard Cairns, said: “These are essential works which could not have been foreseen. We’re now seeking council approval to allow the remediation to be carried out as quickly as possible and this would allow us to get to work on building this fantastic new facility for generations of young people.”

Holmes Miller and Morgan Sindall are behind the campus development.