The measure is being considered by the Department of Health as a means of preventing the congenital disease spina bifida, and is already in force in dozens of countries.
An announcement had been promised by Easter. However the department issued a low-key statement last week, saying it would wait until new evidence was available next year before deciding.
Michael Matheson, Scotland's Minister for Public Health, said: "We are disappointed with the decision of the UK Government not to pursue mandatory fortification of bread with folic acid.
"This is an entirely safe measure already adopted by more than 40 countries around the world.
"All of the evidence, including our advice from the Food Standards Agency, is that this is a simple step that would greatly reduce neural tube defects such as spina bifida."
He said the measure was also supported by the governments of Wales and Northern Ireland, and the Scottish Spina Bifida Association.
"We will be looking carefully at today's decision and considering our next steps," Mr Matheson said.
A spokesman later confirmed this would include looking at the unilateral introduction of folic acid to flour products in Scotland, but ministers would prefer to see a coordinated approach across the UK.
Andy Wynd, chief executive of the Scottish Spina Bifida Association (SSBA), said: "We are frustrated to hear that the Department of Health are stalling yet again on the mandatory flour fortification issue."
"In Scotland it is thought that nearly 50% of pregnancies are unplanned and mothers-to-be will not have increased folic acid intake prior to conception.
"The association believes that mandatory fortification is the only option that will make a significant difference to the many unplanned pregnancies diagnosed with neural tube defects, of which spina bifida is the most common."
Folic acid is a naturally occurring vitamin that is contained in foods including leafy vegetables, citrus fruit, beans, and whole grains.
It can greatly cut the chance of a mother-to-be having a baby with neural tube defects. If the correct amount of folic acid is taken prior to conception, it is estimated that this could reduce the number of spina bifida cases by around 75%.Such defects are one of the most common severe congenital malformations and just over one in 1000 births in the UK have NTDs.
This is one-and-a-half times higher than in the US and doctors believe the difference may be down to fortification of flour with folic acid.
The Medical Research Council says the fortification of 28.9% of the world's industrially milled wheat flour with folic acid is preventing thousands of cases of serious birth deformities and as a result saving large sums of money in healthcare costs.
Scotland has the highest number of live births of babies with spina bifida of any UK nation, with around one baby a week being born with either spina bifida or hydrocephalus or both.
The UK's four chief medical officers, The Food Standards Agency and the Scientific Advisory Committee on Nutrition have all recommended fortification.
A spokesman for the Department of Health said: "We have carefully considered the Scientific Advisory Committee on Nutrition's advice on folic acid.
"With a decision as important as the mandatory fortification of food, it is vital that we take the latest evidence into account.
"We believe we need information on the blood folate status of the population, which will be available in 2015, to inform our decision."