Opposition leader Joseph Muscat is in the Czech Republic for the Congress of European Socialist Parties.
The congress, the first since the European Parliament elections, will discuss the future of progressive societies, the PL said.
They will also discuss climate change.
Dr Muscat is accompanied by Dr George Vella, party spokesman on foreign affairs, Dr Alex Sceberras Trigona, party international secretary and EP election candidates Marlene Mizzi and Maria Camilleri.