Soft drinks companies frustrated at the U.K. government's decision to impose a tax on the sugar in beverages are considering legal action, the industry body told CNBC.

Last week, U.K. finance minister George Osborne announced plans for a . The tax, which will be introduced in 2018, will be paid by producers and charged on products containing more than 5 grams of sugar per 100ml, with a higher rate of tax for products containing more than 8 grams.