The UK Government has claimed Scots would face higher energy bills if the country votes for independence to cover the cost of a £1.3bn electricity link.
Scottish Power is building the 260-mile subsea cable that will connect Hunterston B power station in West Ayrshire with Merseyside and Wales, which is due to be completed in 2016.
UK energy minister Michael Fallon said an independent Scottish government would have to pump more public money into the project to keep it on track, resulting in higher utility bills.
But Scottish finance secretary John Swinney said the single energy market in Britain would continue after independence because the rest of the UK depends on renewable energy from Scotland.
Video - Independence debate reaches new depths with subsea energy link row