The Scottish and Welsh governments are urging Health Secretary Jeremy Hunt to make it compulsory for flour to have folic acid in it.
Senior figures in the two devolved administrations have written jointly to the UK Government on the issue after figures showed roughly four out of five women of childbearing age in Scotland and Wales do not have enough of the key nutrient in their diet.
Food Standards Scotland (FSS) has already said there is clear evidence that fortification flour could help prevent birth defects such as spina bifida and other neural tube defects (NTDs) in unborn babies.
In Scotland, 158 babies were born between 2007 and 2011 who were suffering from such conditions while 131 pregnancies were terminated after these were detected over the same period.
Scottish public health minister Aileen Campbell had asked FSS to look at if the mandatory fortification of bread or flour with folic acid could be done on a Scotland-only basis.
However, it found that for cost and practical reasons this would not be appropriate, and instead recommended it be introduced across the whole of the UK.
Ms Campbell and Welsh Health Secretary Vaughan Gething told the UK Secretary 81% of women in Scotland of childbearing age and 79% of such females in Wales were not getting the recommended amount of folic acid – higher than the 75% recorded across for women across the UK.
The two politicians said: “We are therefore clear that there remains a compelling case for action across the UK to reduce NTD incidence, particularly in the most socio-economically deprived areas.”
They added that recent work by both FSS and the Scientific Advisory Committee on Nutrition had provided ” evidence for taking this forward on a UK-wide basis” – with this view also backed by the Department of Health in Northern Ireland.
Ms Campbell and Mr Gething told the UK Health Secretary: “We want to work together to make this happen.
“We strongly urge you and your ministerial colleagues to reconsider your position and press ahead quickly with a decision on mandatory fortification of flour with folic acid for England, and to agree to a uniform approach to the introduction of legislation across the UK.”
The British Pregnancy Advisory Service (BPAS) also backed the call for flour to have folic acid added to it.
A spokeswoman said: “We strongly support the mandatory fortification of flour with folic acid to reduce the incidence of neural tube defects in the UK, which often result in the termination of a much-wanted pregnancy.
“BPAS urges Mr Hunt to listen to the calls of his colleagues in Scotland and Wales and back this measure – there are very few public health interventions which have such a strong evidence base as this one.”