By Kate Kelland LONDON (Reuters) – Britain on Thursday said it would tax companies which sell sugary soft drinks and invest that money in health programs for school children, part of a long-awaited strategy to curb childhood obesity that critics say is too weak. Drinks companies were also angered by the plan which urges industry to cut sugar in products aimed at children, saying nearly a third of those aged 2 to 15 are already overweight or obese. In a statement announcing details of the strategy, which has been in the works for several years, junior finance minister Jane Ellison said obesity was costing Britain’s National Health Service (NHS) billions of pounds every year.