Primark has stolen a march on High Street rivals by signing up to a Government code that allows it to boast about paying suppliers on time. The discount clothing chain last week formally adopted the Prompt Payment Code, which is being championed by Baroness Vadera in the new Department for Business Innovation and Skills in an attempt to help small firms through the recession.She has already persuaded Asda, Tesco and John Lewis to sign up.But some of the country’s biggest retailers – including Marks & Spencer, Next and Debenhams – have so far failed to back the register, which aims to stop large companies conserving their cash flow at the expense of small suppliers