Dorset based Woodmace also wants to see banks actually lending money to contractors rather than just talking about it.

Woodmace employs 120 staff and has a turnover of £15m.

But the firm currently has £650,000 tied-up in outstanding retention payments which are hitting cash flow.

The retention cash includes £65,000 still being held by the main contractor two years after the job was completed.

Operations director Nigel Cooper has taken his case straight to Number Ten with a letter to David Cameron.

He said: “With main contractors extending payment terms far in excess of 30 days – despite Government stipulating 30 day payment on Government Contracts – we attempted to increase our overdraft facility to a modest £350k only to be turned down unless the figure is matched in personal guarnatees.

“How then can businesses expand, grow and support the economy without the support of the banks and where does this fit in with the Governments intent and determination to boost SMEs?

“When will antiquated payment terms be outlawed by Government, when will retentions be abolished and when are Tier 1 main contractors going to be penalized for their elongated payment terms?

“When will the subcontractor have a voice to be heard at Government level and not be represented by large main contractor organisations only interested in their own well-being?

“The subcontractor after all is the person or organisation actually carrying out the works.

“How can banks and institutions be educated in construction and understand the complex payment terms to fully understand the process and not be scared to lend to thriving businesses?

“Why do we have to put up with outdated and biased payment terms?”