Parents were warned today not to take their children to “swine flu parties” in the hope they will catch the disease and build up immunity.

Although no firm evidence has emerged of such events taking place, family website mumsnet.com has witnessed discussions over whether parents should take steps to ensure their children acquire immunity before the main flu season in the winter.

For years some parents have deliberately exposed their children to playmates with chickenpox in order to allow them to have the once-only disease at a convenient time.

But British medical expert Dr Richard Jarvis has warned against taking the same approach with swine flu.