Valletta, Malta: A prominent Maltese businessman has offered to testify against top government officials over the 2017 murder of journalist Daphne Caruana Galizia, and said the Prime Minister had a conflict of interest in the case.

Lawyers for the businessman, Yorgen Fenech, on Thursday (Friday Australian time) deposited in court a letter to President George Vella formally asking for a pardon.

The wreckage of Daphne Caruana Galizia's car was strewn across a field after a powerful car bomb exploded. Credit:AP

In return, Fenech promised to supply information related to former government chief of staff Keith Schembri, former tourism minister Konrad Mizzi, Economic Affairs Minister Chris Cardona and other people "close to the Prime Minister".

The lawyers for Fenech, who was arrested last week in connection with the killing, said Prime Minister Joseph Muscat should not be involved in deciding the plea for a pardon because he was among "persons who may have an interest for such a pardon not to be granted."