A variety of labelling schemes have emerged
Food labelling could end up being ignored by a large number of shoppers, experts suggest.
A "significant" proportion did not take them into account when buying treats such as cakes, show early results from a Food Standards Agency-funded study.
Researchers said this was because shoppers knew they were bad for them but wanted to "indulge" themselves.
They also found a trend for ignoring them when buying supposedly basic essentials such as flour and butter.
Those surveyed said this was because these ingredients were needed and could not be avoided.
The FSA has funded a group of experts led by Sue Duncan, a former chief social researcher for the government, to look at the influence of the variety of food labelling schemes in existence.
The independent group has also been given the backing of industry and campaigners in an attempt to find a consensus on the issue.
It comes after retailers have adopted a range of approaches.
Some, including the supermarket chain Tesco, are using guideline daily amounts showing the percentage of daily recommended fat, sugar and salt intake each serving contains.
But the FSA has already said it favours a traffic light system where red means high levels of fat or sugar.
And other groups, such as Asda or Sainsbury's, have adopted a hybrid of the two.
The group is not due to publish its final report based on an in-depth survey of 3,000 people until next year.
But the early findings, based on snapshot surveys involving 200 people, found a number of issues.
As well as a tendency for some to ignore labelling when buying treats or basic ingredients, researchers also found people were likely to be influenced by manufacturers health claims such as the product being "low in fat".
To add to the problem, while people took the nutritional information into account when shopping, some were less likely to do so when putting together a meal at home.
The study also showed there was a degree of confusion about the labels being used. Part of this is down to the variation in schemes, but researchers also said some of it was down to the labelling system itself.
Ms Duncan said: "It is too early to draw any firm conclusions, but some trends are emerging."
A spokesman for the FSA said: "From the research so far it's clear that consumers welcome, and want, front-of-pack labelling and are frequently using them to inform their choices."
Jane Holdsworth, the director of the GDA campaign, a coalition of manufacturers and supermarkets, said: "The debate about which labelling format is preferable could continue indefinitely but clearly, the real challenge here is reaching consumers who simply do not look for nutrition information at all.
"This is where we should all focus our efforts going forward."