The head of construction at NBN Co, the government-owned enterprise building the $36 billion National Broadband Network by 2020, has resigned.

Patrick Flannigan had been in charge of implementing the most expensive part the company's vast mission: laying a network of fibre optic cables to deliver broadband speeds of 100 megabits per second to 93 per cent of Australians.

The country's telecommunications industry was shocked to learn late last week that NBN Co had written to 14 construction firms announcing that after five months of negotiations, the NBN's lucrative tendering process was indefinitely suspended.

Hinting the firms were seeking to "price gouge" the project, the NBN's head of corporate services Kevin Brown said all the received quotes were overpriced in the "double digits".

Now in the latest blow to NBN Co's efforts to deliver the project on time and on budget, the company's experienced head of construction, Mr Flannigan, tendered his resignation yesterday.

Mr Flannigan managed the construction of the NBN's first release sites in Tasmania.