One of the companies building the national broadband network has collapsed, citing a lack of work from Australia's largest infrastructure project, with an estimated 250 jobs at risk.

Melbourne-based civil and mining services company Techdrill entered voluntary administration on Tuesday. More than 50 full-time staff are expected to lose their jobs. Fairfax Media has been told that several hundred sub-contractors could also be impacted, mostly in NSW and Queensland.

Techdrill is said to have been 'squeezed' after hiring staff and subcontractors for NBN work that never materialised. Credit:Glenn Hunt

A source close to the company - which has been digging trenches to install fibre optic cable for the $41 billion project in NSW and Queensland - said it had been "squeezed" after hiring staff and subcontractors for NBN work that never materialised.

NBN Co's move from away from Labor's plan to connect fibre optic cabling to 93 per cent of Australian homes and businesses has resulted in much less digging and drilling for pits and pipelines. It is understood the amount of work Techdrill originally signed up for with Downer has evaporated, as NBN Co's new management seeks to hasten the NBN roll-out by using Telstra existing copper network.