The Federation of Small Businesses in Wales has called on Welsh politicians to give a commitment to tackle the issue of late payment.
An estimated £40 billion was owed to smaller firms in late payments last year.
FSB Wales said it is concerned at the huge impact the culture of late payment is having on small businesses.
FSB Wales Policy Chair Janet Jones said: “The time has come to address this issue once and for all.
“The abuse of small firms in their dealings with bigger businesses can’t continue. We have seen the UK’s payment culture significantly deteriorate in the past five years. The gradual creep of payment terms from 30 days to well over 100 days in some cases, coupled with debilitating contract terms, can have a disastrous effect on a small firm’s ability to operate.
“With the election almost upon us our members would be keen to hear how each of the parties would deal with this pressing issue.”