Schools, hospitals, prisons and other public buildings will have to generate at least one-fifth of their energy under Liberal Democrat election plans.

The prospect of wind turbines and solar panels would become a feature of many town centres, as well as biomass generators in public buildings.

Nicol Stephen, the Scottish LibDem leader, set out part of his renewable energy manifesto yesterday, while also announcing an executive allocation of £4m to help universities and colleges become more energy efficient.

This extends a £20m fund for local authorities, NHS boards and Scottish Water spent since 2004.

The longer-term party plans, to be included in the LibDem manifesto, are for all Scottish Executive buildings to be carbon neutral by 2011.

Mr Stephen wants to extend that to all other public sector buildings, so that there is a "zero carbon government".

Mr Stephen's promise of executive spending before the election and a party commitment for after it follows Labour leader and First Minister Jack McConnell promising on Monday to cut his use of short-haul air travel on official business. Mr Stephen went further, saying London flights should only be used on executive business "in the most exceptional circumstances".

Labour wants to examine the prospects for individual carbon accounts for each voter.

The party risks alienating the agriculture lobby with its toughest measures aimed at linking farm subsidy to emission cuts.

Scottish Greens accused Mr Stephen of "electoral gimmicks and games".

Co-leader Shiona Baird said: "Today we get another green promise - tomorrow it will be a climate-wrecking promise in the shape of bigger roads and bigger airports."