SCOTLAND'S spending watchdog has warned it could cost £11 billion to meet the SNP Government's climate change targets.

It also said the Government had not yet established how much of the bill would have to be met by individuals, the public and private sectors, nor had it prioritised its policies on their cost-effectiveness.

The Audit Scotland report, Reducing Scottish Greenhouse Gas Emissions, said that, where the Government had estimated the cost of its policies, the figures were associated with "significant uncertainties" including long-range forecasts and fuel prices.

The report said there has been a fall of more than one-quarter since 1990 but the target of reducing emissions by 42% by 2020 was far greater than UK or European Union goals.

The UK target is 34% and the EU's 20%.

The Scottish Government's plans include action to reduce emissions from vehicles, improve the energy efficiency of homes and buildings and increase the rate of tree planting.

Auditor General Robert Black said: "To meet the 2020 target, new policies will need to be delivered successfully – especially in transport.

"The challenges will be that much greater over the next few years when the pressures on Scotland's public-sector finances are likely to increase."

Green Party co-leader Patrick Harvie blamed successive governments for the costs because of their failure to take early action.

He said: "The cost of cutting CO2 emissions is still far more affordable than the much greater cost of doing nothing."

Shadow Energy Minister Tom Greatrex predicted the cost would rise further if Scotland separated from the rest of the UK.