The Melbourne Storm have asked the NRL for a please explain after an embarrassing refereeing error that could have had major ramifications on the outcome of Saturday night's preliminary final.

While it didn't end up costing them, the Storm have asked the NRL why Cameron Smith was forced to attempt a conversion – and missed – 10 metres wider from where Cheyse Blair had scored in the 60th minute of the match against Canberra at AAMI Park.

Picture 1: Cheyse Blair crosses to score for the Storm and is clearly some metres infield from the 'tram track', which is visible at the top right of screen. Credit:Fox Sports

In a finals series that has been marred by controversial officiating, the NRL avoided another black eye given the Storm held on to book their passage into the grand final, but it still could have a major impact on the selection of the referees for the decider between Cronulla and Melbourne at ANZ Stadium on Sunday.

The blunder could have proved costly, given Smith missed what should have been a simple conversion that would have taken Melbourne out to an eight-point lead with a quarter of the match remaining.