Outgoing prime minister Joseph Muscat has pulled out of a Rome migration conference "at the last minute", according to Deutsche Presse-Agentur. 

Dr Muscat was due to speak about migration at the MED 2019 conference, an annual high-level initiative promoted by the Italian government. 

Instead he has been replaced by his foreign minister.

There have also been reports of Italian premier Giuseppe Conte cancelling a lunch with Dr Muscat, ostensibly due to scheduling issues. 

The embattled prime minister is also set to have a private audience with the Pope on Saturday, despite calls for the meeting to be cancelled in light of the growing scandal consuming the government. 

Dr Muscat has pledged to step down in January, although there is mounting pressure for him to bow out immediately. 

As Dr Muscat takes one of his last trips as prime minister abroad, key figures in the Labour Party have thrown their weight behind Chris Fearne as his potential successor. 

Dr Muscat's former chief of staff Keith Schembri was recently questioned in connection with journalist Daphne Caruana Galizia's assassination. 

Businessman Yorgen Fenech, one of the lead businessman in the power station project pushed by Labour in 2013, has been accused of complicity in Ms Caruana Galizia's murder.

Mr Fenech has in turn accused the former chief of staff of being a co-conspirator in the murder plot. 

Middleman Melvin Theuma, who was granted immunity from prosecution by Dr Muscat, this week said a former member of Dr Muscat's security detail relayed a message about passing on money to the three people accused of carrying out the bomb plot.