Widdop, 22, has featured more regularly in the Storm first team this season, having played three times last season. He made his England debut against France last year, and also featured in the end of season Four Nations.
He was one of six players who featured in the side that beat South Sydney on Sunday who are on the minimum wage.
Adam Woolnough, Jesse Bromwich, Sisa Waqa, Rory Kostjasyn and Maurice Blair are the other players on the basic income at the club, that was stripped of two premierships for spending too lavishly in recent seasons.
Coach Craig Bellamy said: “The leadership group have done a great job getting the best out of these guys.”