By Gwladys Fouche

OSLO, Dec 2 (Reuters) - Norway's $1.8 trillion wealth fund's ethics watchdog will next year investigate shoe manufacturers, cryptocurrency companies and casino and gambling firms for possible ethical breaches, which could lead to the fund making divestments.

The world's largest sovereign wealth fund, which has massive market influence as it owns 1.5% of the world's listed shares across 8,700 companies, operates under ethical guidelines set by parliament.

The fund's ethics watchdog, the Council on Ethics, investigates companies the fund is invested in to ensure these guidelines are respected. If they are not, the council recommends the fund divests from these companies or put them on a public watch list.

"During 2025, the council will investigate work conditions at a significant number of shoe producers," said a document drafted by the council and sent to the finance ministry on Oct. 10.

"Companies have a direct responsibility for working conditions within their own operations and gross, systematic breaches of workers' rights can lead to exclusions from the fund."

The plan, seen by Reuters, has not been previously reported. It did not name specific companies.

The Council on Ethics told Reuters that "the work programme for 2025 indicates that these are issues the Council will look into in 2025.

"It is not possible for the Council to predict the outcome of the investigations," it said in an emailed statement.

(Reporting by Gwladys Fouche in Oslo, editing by Terje Solsvik)

((gwladys.fouche@tr.com;))