A claim that a formula baby milk can improve an infant's eyesight is being challenged in Brussels - despite having been approved by EU food health experts.
A senior British MEP has stepped in just days before a February 3 deadline for raising objections.
Authorisation for the eyesight claim was given by the EU Standing Committee on Food Chain and Animal Health in a private meeting last December.
It relates to a declaration by American-based formula baby milk manufacturer Mead Johnson about the benefits of its milk products containing a fatty acid called DHA.
The Committee, made up of national food health specialists from the 27 EU countries, has power to decide whether health claims used in the marketing of food and drinks could mislead the public.
And the experts have backed Mead Johnson's statement that "DHA has a structural and functional role in the retina, and DHA intake contributes to the visual development of infants up to 12 months of age".
But now the leader of Britain's Labour MEPs, Glenis Willmott, is invoking European Parliament powers to question the decision.
Ms Willmott, the party's euro-spokeswoman on food safety, commented: "It is clear that there are concerns about the scientific evidence that would support a claim like this.
"We simply don't know enough about how DHA functions when delivered via the bottle.
"If this particular fatty acid is really proven to be beneficial to babies' health when used in formula milk then we owe it to mothers and their children to ensure it is included in all products. If the link hasn't been proven, then companies shouldn't be allowed to make this claim."
DHA - "docosahexanenoic acid" - is found in small amounts in breast milk and is a recognised factor in the development of infants' retinas.
But Ms Willmott says there is no consistent independent evidence that the synthesised version of DHA used in formula milk - different from that found in breast milk - has the same eyesight benefits.
She wants the issue reconsidered by the European Parliament - with a majority vote of all 736 MEPs required to overturn the experts' decision.
Ms Willmott added: "The European Parliament delegated the power to make these decisions to a specialist committee, but most of the work done under the health claims legislation focuses on foods for adult consumption."
The same expert Committee has rejected a series of other claims by manufacturers about the benefits of formula baby milk, but Ms Willmott is concerned that its decisions are made in private. Summaries of its meetings are published, but the votes of the various national specialists are not shown.
Ms Willmott said: "Baby milk is a very special product and this decision has been taken without public scrutiny. I want to have a proper debate about whether this kind of claim is appropriate and I want to have that debate in public."
She said the issue was separate from the "breast is best" debate, adding: "I recognise that there are clear benefits to a child's development in breast feeding, but in this case I want to ensure that parents who choose to bottle feed can be confident that manufacturers have parents and their children's best interests at heart.
"I am sure that milk manufacturers will be gearing up for a big battle on this issue but our children's health is too important to be left in the hands of a multinational company's marketing department."