Sales at British Polythene grew 12.5% last year but profits were affected by higher input costs.The company, which manufactures polythene products for various markets including agriculture and packaging, saw revenue grow to £478m, from £425m as the construction and industrial sectors rallied while there were robust sales of agricultural stretch-film.Operating profit decreased to £17.9m, from £19m, due to the delay in passing higher raw material costs onto customers.However a restructuring - which meant a £3.8m gain on the sale of its Brompton and Stockton sites - saw pre-tax profit grow to £16.7m, from £11.8m in 2009."Despite increases in raw material costs of some £45m, operating profits were only £1.1 million less than 2009. The Board is encouraged by this very satisfactory performance in difficult circumstances and are recommending an increase in the dividend for the year," said chairman Cameron McLatchie.Basic earnings per share increased from 30.86p to 52.2p, while the total dividend grew to 11.5p, from 11p.