Manly coach Geoff Toovey says Canterbury deserve to be the most penalised teams in the NRL as scrutiny of the Bulldogs' controversial decoy plays intensifies ahead of the finals.

Toovey has been a vocal critic of the way the obstruction rule has been policed throughout the season and said he still held reservations about Canterbury's style of play heading into Friday night's qualifying final.

"If anyone pushes it to the letter of the law it is probably the Bulldogs and I think they are the most penalised team in the competition for good reason," Toovey said.

"They play a lot of second phase stuff, with their decoy runners interfering to give Benny Barba a bit of space out wide and I'm sure it is something the referees will look at.

"Those decoy runners are checking defensive players and that could be vital in the semi-finals.

"It's those little things they need to be focusing on come semi-finals because it could cost a team some points."

Of the eight finals teams Canterbury were by far the most penalised during 26 regular season rounds with 152 penalties conceded.

Manly were the next worst offenders conceding 133 penalties with Canberra third (124).

After the Bulldogs were awarded a contentious try against the Tigers in round 24, which was later ruled to have been the wrong call, referees boss Bill Harrigan has moved to clarify the obstruction rule.

Harrigan sent a detailed DVD to all clubs to outline what would and wouldn't be allowed.

He also gave his referees a crash course in policing the rule.

Last week Sydney Roosters repeatedly claimed Canterbury ran illegal plays in their 42-10 win.

But Toovey said he was confident the referees had finally formed a common sense and workable approach to the obstruction rule and said he wouldn't bring the issue up with Harrigan prior to the finals.

"I have done a bit of that in the past, it hasn't helped much," Toovey said.

"I'm sure, hopefully, it won't be a problem in the semi-finals.

"I think they (the referees) are smart enough to know, they have done enough research, I am sure they are on to it.

"It has been a clouded area throughout this year.

"The only thing I am disappointed about is that it has taken this long to do something about it. It is probably a bit late."