The 34-year-old was sin-binned for the series of punches, which were in retaliation following a headbutt on his brother Sam by Wigan full-back Zak Hardaker towards the end of the game in Perpignan.
Hardaker, who was sent off, was subsequently given a two-match ban for what the Rugby Football League’s match review panel said was a Grade C offence.
Tomkins was charged with a more serious Grade D offence, which the panel described as “sustained, repeated or violent” punching, and normally carries a ban of between three and five matches.
The player entered a guilty plea when he faced a tribunal hearing on Tuesday evening but challenged the grading of the offence. However, the tribunal found the grade to be correct and, in addition to a four-match ban, he was fined £500.
It was only his fifth game back from an eight-match ban carried over from last season after he was found guilty of “inappropriate contact” on the backside of Leeds full-back Richie Myler.
Meanwhile, Castleford forward George Griffin will miss Saturday’s Challenge Cup semi-final against Warrington after a one-match ban for a dangerous tackle in his side’s 60-10 home defeat by Leeds was upheld on appeal. He was also fined £500.