Work has stopped on the national broadband network in Ballarat, Victoria, following a dispute with sub-contractors, as ongoing problems plague the network.

The Ballarat dispute – which escalated on Monday – comes on the same day as contractors in Tasmania are holding crisis talks that will determine whether they continue rolling out the NBN.

These disputes are part of a larger, and worsening, headache for NBN Co. Major contractors appear to be struggling financially and subcontractors are downing tools because they are angry about not being paid on time, or in some cases, not being paid enough, for their work.

The increasing number of contractual disputes raises questions about whether the cost of building the NBN – currently estimated at $37.4 billion – could blow out as the Coalition has been predicting.

On Monday, all work on the NBN in Ballarat, in regional Victoria, halted, after a second major sub-contractor downed tools in the space of two months. It is understood the two subcontractors, Australian Broadband Company and DirectBor, are complaining about the same problem – that main contractor Transfield Services is not paying them on time.