UK Labour Party deputy leader, Tom Watson, called on the UK foreign secretary, Boris Johnson, to challenge Prime Minister Joseph Muscat regarding the lack of action taken by the government to solve the murder of Daphne Caruana Galizia.

The Guardian reports that Watson called on Johnson to highlight “this very serious case … It is clear not enough progress has been made in the investigation of this terrible murder.”

Caruana Galizia was killed in a car bomb on 16 October. Three men have been arraigned in connection with the murder.

Watson’s call comes as Prime Minister Joseph Muscat is in London to take part in the Commonwealth Heads of Government Meeting. Malta holds the presidency of the Commonwealth.

Malta and the Prime Minister have been under fire since Tuesday following stories published by a consortium of media houses that investigated stories covered by Caruana Galizia.

The UK Labour Party is part of the Socialist and Democrats group in the Eurpoean Parliament, the same group as Malta’s Labour Party.