A slanging match erupted last night in the Senate's environment and communications committee during the appearance of the NBN Co at an estimates hearing.

In a tense exchange, Liberal Senator Bill Heffernan swore at Communications Minister Senator Stephen Conroy who then suggested that Senator Heffernan had been drinking.

The barbs started flying after Liberal senator Simon Birmingham expressed his frustration that NBN Co chief executive Mike Quigley was not able to provide enough detail about the roll out of the NBN - despite having questions on notice since last October.

Senator Conroy then suggested that Senator Birmingham was ''too lazy'' to look for the detail himself on the NBNCo website.