Parents will be told not to give most cough and cold remedies to their children amid safety fears and evidence that dozens of products do not work.

More than 60 popular over-the-counter medicines, some specifically labelled for children, will be marked with warnings that they must not be given to children under six and are not recommended for under-12s.

In an unprecedented move, Government safety regulators will advise that the dangers posed by the remedies outweigh any benefits.

Several children have died from overdoses of the medicines, while others have suffered hallucinations, allergic reactions and other side effects.

The alert centres on 15 ingredients found in most cough and cold medicines, many of which have been used by drug companies for years.

The deaths of at least five children under two have been linked to the remedies and more than 100 serious cases of suspected adverse reactions have been reported, with children requiring hospital treatment.

Five products aimed at children younger than two have already been withdrawn.

The Medicines and Healthcare Products Regulatory Agency (MHRA) said last night that a review of 69 cough and cold remedies for children had "found no robust evidence that these medicines work" and gave warning that "they can cause side effects, such as allergic reactions, effects on sleep or hallucinations". There has been growing concern about cold remedies for children, particularly when parents miscalculate the dose, give additional doses or combine products containing similar ingredients.

By March next year, all over-the-counter cough and cold remedies containing the 15 ingredients will have warning labels on their packaging. Until then, notices will be placed on shelves advising that they should not be given to children under six and should only be given to those aged six to 12 after consulting a pharmacist. Chemists will be told to caution against their use for children under 12, unless there are special reasons. Some products should never be given to under-12s.

Reports submitted to regulators show that, when cases involving people of all ages are considered, dozens have died after taking medication containing the ingredients and more than 3,000 people have reported "adverse reactions". Diphenhydramine, which is used in Benylin Children's Coughs and Colds, was mentioned in reports of 27 deaths, while chlorphenamine, an ingredient in Tixylix Cough and Cold, was mentioned in reports of 11 deaths.

Parents will be advised to give temperature-lowering drugs such as paracetamol to children with colds, and to use a simple cough syrup containing glycerol, honey or lemon, with vapour rubs for a stuffy nose.

Martin Shalley, a consultant in emergency medicine at Birmingham Heartlands Hospital, said of the remedies: "The names are confusing and often sound very innocuous; the dangers are only in the small print, and on top of the risks, there is no evidence that any of these products do any good."

Dr Hermione Lyall, a consultant paediatrician at St Mary's Hospital in London, said: "These drugs carry a number of risks; they can affect the heart, speeding it up or down, and they can even affect the central nervous system, leading to convulsions.

"Coughs and colds will run their course and if you are going to use any medication it is much better to rely on paracetamol or ibuprofen to reduce a child's temperature."

The ingredients involved are: the nasal decongestants pseudoephedrine, ephedrine, phenylephrine, oxymetazoline and xylometazoline; the antihistamines diphenhydramine, chlorphenamine, bromopheniramine, promethazine, triprolidine and doxylamine; the cough suppressants dextromethorphan and pholcodine, and the expectorants guaifenesin and ipecacuanha.

Dr June Raine, from the MHRA, said that although many of the products have been used for years, trials into their safety and effectiveness had not been carried out on children.