The BBC Question Time debate also saw fiery exchanges on climate change, electoral reform and trust.
But the Tories attack Labour's spending plans and warn of a hung Parliament, two days before the election.
The UK high commission in New Zealand says two Britons caught in the volcano eruption are now in hospital.
Drax, which generates 5% of UK power, says it will capture more carbon than it produces by 2030.
The fire broke out on Glasgow's Lancefield Quay on the north bank of the Clyde on Monday evening.