Just before he dethroned Tony Abbott to become Prime Minister, Malcolm Turnbull phoned long-time rival and independent telecommunications analyst Paul Budde.

Budde had written a negative analyst note on August 25 about the now former communications minister's oversight of the national broadband network, saying he "simply didn't have a clue what he was doing" by changing "such a large national infrastructure building project midway through the process". Budde revealed the call in a note sent to journalists last Wednesday.

Turnbull, who had previously taken issue with Budde's NBN analysis, was apparently so incensed by the analyst's note that he felt the need to call Budde. When exactly the call was made is not known, and neither is what Turnbull said.

But Budde offered a clue: "He invited me for a deeper discussion [about various issues around the NBN]; I think the time might be ripe to review the NBN and start adding the [fibre-to-the-home] extension to it."