Andy Burnham, the health secretary, was ambushed live on breakfast television today over the government's policy of giving Tamiflu to children when the GMTV presenter Andrew Castle told him his own daughter had almost died after taking the antiviral drug.

Castle said his 16-year-old daughter, Georgina, suffered a respiratory collapse after being handed the drug at school without having been properly diagnosed.

He told Burnham: "I can tell you that my child – who was not diagnosed at all – had asthma, she took Tamiflu and almost died. We saw a respiratory collapse through it and it almost cost my older child her life.

"Nobody checked that she had swine flu beforehand. The Health Protection Agency just handed it out at the school. We suffered, Georgina suffered and a lot of kids suffered in the school very heavily."

Burnham told the presenter: "It must have been a very worrying situation for you, but that was in a very different phase of the illness when we were seeing the scenes from Mexico and we were in what we call the containment phase, where we were trying to isolate every case and then give Tamiflu to those around those cases."

Seeking to reassure families, the health secretary said that parents ought not to be worried about giving their children antiviral drugs if they have the illness. He stressed that research published yesterday had looked at seasonal flu, not swine flu. Given that swine flu had a disproportionate effect on children, he said the government had adopted a safety-first approach. He added: "Tamiflu is our best line of defence against what is a new virus."

Yesterday's study, carried out by scientists from Oxford University and published in the British Medical Journal, concluded that children should not be given antiviral drugs Tamiflu or Relenza because their side-effects, such as vomiting leading to dehydration, outweigh any benefits.