The current system for providing free nursery care for youngsters has been branded "grossly unfair".
Independent think-tank Reform Scotland made the claim in a new report which said some children could receive almost one year less of government-funded nursery education, depending on when their birthday falls. It has now called for all youngsters to receive two full years of funded nursery provisions.
To achieve this, it suggested government-funded provision for all youngsters should begin at a fixed point in the year - probably August - two years before children start at school
"Every child should be entitled to two years of government-funded nursery provision, regardless of when their birthday falls," Reform Scotland said.
Alison Payne, research director at the think-tank, stated: "This is a question of equality. It cannot be deemed to be fair that children and hard-pressed families are offered such widely divergent periods of funded nursery provision purely because of when the child's birthday falls."
Youngsters can currently receive 475 hours a year of free nursery care, although the Scottish Government has already pledged to legislate to increase this amount to 600 hours.
At present, government-funded nursery education begins from the start of the term after a youngster's third birthday. That means children born between March and August will start nursery in the August term, and could receive two years of funding before they start school.
But youngsters born in January or February would not receive funding until the summer term commences in April, and assuming they start school at the age of four-and-a-half, would only receive 15 months of free nursery provision.
A Scottish Government spokesman said: "Our Children and Young People Bill aims to provide more high quality early learning and childcare for children than ever before, providing children in Scotland with the best start in life.
"The Bill also aims to provide greater flexibility of provision to meet the needs of children and their parents. We are aware of this particular issue and it is part of our wider considerations around the forthcoming Bill."