Manchester firm is alleged to owe sub-contractors thousands of pounds after work carried out on fibre-optic network.
Several sub-contractors brought in to work on the £30 million Fibrespeed project linking Wales to England by cable broadband are still waiting to be paid.
The network connected businesses in north Wales with high-speed services a 200-mile line reached over the border as far as Manchester.
"It is one of the biggest utility contracts in the country and we thought with the present climate that there is plenty of work to go out but obviously we haven't been paid for it," one dismayed sub-contractor told the BBC.
Continuing: "We have been at the work since mid summer and we have worked very hard but payment has not been forthcoming."
It is thought that Manchester-based United Formwork owes a substantial amount of money for work already carried out.
Fibrespeed will act as wholesaler to UK ISPs, which will have the ability to offer super-fast cable broadband services.