Victoria's Premier Denis Napthine has conceded it was an "error of judgement" for one of his MPs to write a character reference for a man convicted of child pornography offences.

Mildura Nationals MP Peter Crisp wrote to Corrections Victoria in 2011 urging it to allow the man to travel overseas to Turkey.

This comes after Mr Crisp was charged with firearms offences, which he says he will vigorously defend.

Dr Napthine says it was a mistake for Mr Crisp to write the reference, but he has the Government's full support.

"Mr Crisp has been a member for Mildura since 2006, he is a very very hard working and effective member for Mildura.

"He is a compassionate man, he is a man who really fights for his local community," the Premier said.

"Mr Crisp himself has put out a statement today saying it was an error of judgement, it certainly was something I wouldn't have done.

"He has apologised to myself, the Deputy Premier and to anybody else who may have been hurt by the actions he took," Dr Napthine said.