MILAN, Feb 22 (Reuters) - Workers at Italy's biggest utility Enel will go on strike on March 8, accusing the group of planning to outsource core business activities, shrink investments and slash labour costs, three trade unions said on Thursday.

The protest will halt activity at Enel's production sites one by one, without jeopardising the power service, unions CGIL, CISL and UIL said in a statement.

"The reasons for the dispute remain the same: an inadequate and damaging business plan, a lack of investment, indiscriminate cuts in labour costs, outsourcing of core activities and worsening working conditions for Enel's 30,000 Italian employees," the unions said.

Unions and Enel's top management are also at loggerheads over potential changes to the group's rules for working from home, workers representatives have said.

Enel was not immediately available to comment.

In November, Enel's top management said the group planned 35.8 billion euros ($38.7 billion) of gross capital expenditure to 2026 and would cut costs by 1.2 billion euros in the period to 2026 compared with the level of 2022.

($1 = 0.9249 euros) (Reporting by Francesca Landini Editing by Mark Potter)