NATIONAL parliaments in eight European Union countries have come out against the proposal to have a single system for companies based in the European Union to calculate their tax.   One parliament, Portugal, is in favour.   Those against were the UK, Ireland, the Netherlands, Bulgaria, Sweden, Poland, Malta and Romania.   However, the number falls short of the one-third of countries needed to force the European Commission to withdraw or adjust the draft Common Consolidated Corporate Tax Basis (CCCTB) proposal.