The number of large firms pledging to pay smaller businesses promptly has tripled since a Government drive to tackle late payment.
A growing number of companies in the FTSE 350 have signed up to a new code on prompt payment, taking the total to 126.
Three-quarters of FTSE100 companies have signed up, said Business Minister Michael Fallon, adding: "Late payment is a real issue for businesses across the country.
"It is not fair and poor cash flow can prevent small firms growing and even push them into insolvency. We need to improve the payment culture and I welcome the response of big businesses in signing up to the commonsense principles in the Prompt Payment Code.
"Signing up demonstrates a serious pledge to pay promptly. Reports of any companies found to be falsely committed to the value of fairness in the code will be taken very seriously."