MILAN, Aug 22 (Reuters) - Italian prosecutors have asked for a case to be dropped against former energy transition minister Roberto Cingolani over the alleged abuse of office in granting a licence to a Solvay chemical plant, a document seen by Reuters showed.

In the document, Rome's public prosecutor's office told Cingolani that he was under investigation, but also that the prosecutors had asked for the case to be dropped because of a lack of evidence.

The former minister and current CEO of Italy's state-controlled defence and aerospace group Leonardo is entitled to submit his pleadings or ask to be heard by a panel for ministerial offences in a Rome court.

The panel would then decide whether to grant the prosecutors' request and drop the case.

Cingolani and Leonardo declined to comment.

On Monday two sources with direct knowledge of the matter said Cingolani was under investigation for renewing an environmental permit for the Rosignano Solvay plant on a Tuscan beach in 2022.

The investigation, which does not involve Solvay, followed a lawsuit filed in 2022 by Giuseppe Bivona, activist co-founder of Bluebell Capital Partners, and Elio Lannutti, a former senator of the 5-star movement.

They complained the minister had extended authorisations for the chemical plant, although a source close to the former minister, speaking on condition of anonymity, said the authorisation was a new authorisation, not an extension of the permit that would have expired in 2027.

The source said the new licence was required by law because a change had occurred at the Belgian chemical group's plant.

In September 2022 Solvay said it was planning to reduce the volume of industrial waste discharged into the sea from soda-ash production on the Tuscan coast following pressure from environmentalists. (Reporting by Emilio Parodi, editing by Barbara Lewis)