NICOLA Sturgeon has said she is "cautiously optimistic" that a global deal on climate change is imminent, but returned home from a UN summit in Paris to stinging criticism of her own Government's renewable energy policy.

The First Minister, who represented Scotland at the meeting of world leaders in the French capital, has claimed that her administration is setting an example to the world by imposing tough targets on greenhouse gas emissions and renewable energy generation.

She also won plaudits after announcing that a fund to help communities in third world countries deal with climate change would double to £12 million over four years.

However, a leading economist has accused the Scottish Government of focusing too much on electricity and ignoring other important areas that could lead to a reduction in greenhouse emissions at home.

Tony Mackay, who has specialised in energy economics for three decades, also said that progress with offshore wind farms in Scottish waters had been "very disappointing" with progress on marine and tidal energy "even worse".

He said that while a lot of electricity was being generated from renewables, mostly onshore wind farms, far more needed to be done to reduce reliance on oil and gas on roads and in homes.

In a submission to Holyrood's economy, energy and tourism committee, he said: "Renewable energy is very important for electricity generation in Scotland but it could also make a much greater contribution to other demands such as transport and domestic energy consumption. I believe that these issues have been neglected by the Scottish Government and other bodies.

"For example, biofuels could replace some of the petrol and diesel used for road transport... but there has been little interest in Scotland. I also believe that we should do be doing much more to reduce transport demand, notably through better public transport.

"Similarly, I believe there is great potential for reducing gas consumption in the domestic sector in Scotland but regrettably that is a low priority of the Government."

Mr Mackay also backed the UK Government's move of cutting subsidies for onshore wind, saying foreign companies and landowners had made "supernormal profits" and that the cash could now be better spend in supporting new technologies.

He added: "I am strongly in favour of public sector investment in energy research and development (R&D), particularly for marine energy. However, the R&D funds to date have been badly managed and resulted in huge losses of public sector money."

The Scottish Government has said it wants renewable sources to generate the equivalent of 100 per cent of Scotland's gross annual electricity consumption by the end of the decade, a target Ms Sturgeon highlighted yesterday while in Paris.

The SNP leader added: "Scotland is leading by example when it comes to tackling climate change - we've got some of the toughest statutory emissions reduction targets anywhere in the world, and we're on track to meet them, we're already generating roundabout half of our electricity demand from renewable energy... so there's much we are doing that others can look at and learn from. Equally, we've got a lot to learn from others, we've got a long way to go."

Patrick Harvie, the Green MSP and his party's economy and energy spokesman, said that the Scottish Government should be doing "much more" to improve public transport, reduce energy demand in housing and support marine energy research.

He added: "Shifting to sustainable transport has never been a priority for any Scottish Government since devolution began, yet the evidence is clear that investing in sustainable and active transport delivers benefits in terms of public health, social justice, the economy and climate change emissions.

"Mr Mackay’s evidence underlines the Scottish Government’s more-of-everything energy strategy when a responsible strategy would be transition towards clean technology, decommissioning and demand reduction and away from fossil fuels, a point the unions working in the oil and gas sector recently agreed with me on in committee."