Complex sentence: Only two parties, Alliance of the Democratic Left-Labour Union and Social Democracy of Poland, (both Social Democrats) support the bill, while Citizens Platform, League of Polish Families and Law and Justice (all conservative) opposed it.
Split into simpler sentences: Only two parties, Alliance of the Democratic Left-Labour Union and Social Democracy of Poland, (both Social Democrats) support the bill. While Citizens Platform, League of Polish Families and Law and Justice (all conservative) opposed it.