Dumped Turnbull government frontbencher Stuart Robert will repay around $1600 he billed taxpayers to attend the opening of a mine owned by a company in which he owned shares.

In a letter to the Department of Finance on Tuesday, Mr Robert defended the legitimacy of his April 2013 trip but said he would repay the money to avoid any perception of a conflict of interest.

Stuart Robert says he wanted to ensure there was no perception of a conflict of interest. Credit:Stefan Postles

Mr Robert was forced out of the ministry last week after revelations he attended the signing of a mining deal involving a Liberal donor when travelling in a "private capacity". Mr Robert also owned shares in the company involved in that deal.

It was reported on the weekend that Mr Robert spent $1091 of taxpayers' money to travel from Brisbane to Townsville to visit the $200 million Mt Carlton, operated by gold producer Evolution Mining. He spent a further $580 on Comcar limousine rides and travel allowance. A year earlier, Mr Robert had declared ownership of Evolution Mining shares for him and his family.