A former Telstra executive believed to be working on NBN Co's strategic review still has a $1.5 million stake in Telstra, presenting a potential conflict of interest.

Justin Milne has reportedly started working inside NBN Co along with another former Telstra executive, JB Rousselot, conducting a strategic review to help the new government decide how to proceed with the NBN rollout. This includes whether NBN Co should renegotiate a multibillion deal with Telstra, which could potentially benefit shareholders.

Mr Milne still owns 305,000 Telstra shares, worth about $1.5 million at Tuesday's closing price of $5.01, according to a search of the company's share registry by Fairfax Media on Monday. The shares appear to be part of Telstra's 2006 and 2010 bonus program and were no longer restricted.

A spokesman for NBN Co said it would not ''comment on rumour and speculation'' on staff appointments.

A spokesman for Communications Minister Malcolm Turnbull said staff appointments were a matter for NBN Co. Mr Milne has not responded to requests for comment.