The ICC said Lakmal showed “no remorse” for his actions in the 50th and final over of England’s innings in Sri Lanka’s nine-wicket World Cup win on Sunday.
Lakmal bowled a second consecutive high, full pitched ball to wicket-keeper Buttler, after being given a first and final warning by on-field umpire Rod Tucker during the same over.
Lakmal was stopped from bowling in Wellington and reported to the match referee David Boon for dangerous and unfair bowling.
He was also fined 30% of his match fee after pleading guilty to breaching rules that relate to “conduct contrary to the spirit of the game”.
Lakmal ended the match with figures of 1-71 from 7.4 overs.