Full-time pre-school places will help tackle social inequalities, Children in Scotland has told MSPs as the Prime Minister called the General Election for May 5.
Current commitments on pre-school education and care cover only part-time places.
Children in Scotland is pressing the Scottish Parliament's education committee, which is holding an inquiry into the early years, to back free full-time education for all three and four-year-olds.
Bronwen Cohen, chief executive, said: "Scotland now needs its own clear vision of what is being aspired to with a strategy that builds upon existing services and policies, and works towards achieving universal services for children that integrate care and learning. The most logical step would be to extend the current part-time provision to full time."
Downing Street has already set out a 10-year strategy which promises 3,500 children's centres in England and Wales by 2010. All children will be entitled to 15 hours of a publicly funded nursery place, up from the current 12.5 hours, within five years.
The most authoritative early years research shows that the best provision is managed and run by teachers in local authority nursery schools and integrated centres. The effects last at least two years into primary education.