NRL head coaches have been put on notice in an edict about on-field discipline, warned that referees would not hesitate to march players guilty of repeated infringements this season.

Whistleblowers have been criticised in the past for not following through on threats to use the sin bin and being too lenient, particularly on infringements made by teams defending their own try line, but in an email to the competition's 16 coaches on Tuesday, referees boss Tony Archer declared they would not be shy about taking strong action when round one begins on Thursday week.

"In the past if we haven't taken action we should have been stronger in those cases," Archer told Fairfax Media on Tuesday night. "I think it would be fair to say in 2014 and 2015 we didn't sin bin enough for professional fouls and repeated infringements but I think in 2016 we certainly got to where we need to be for a professional foul, and we need to get to that position for repeated infringements."

Archer's pre-season directive to coaches – which also noted an increase in upright tackles in the trials – will be welcomed by those who have rallied against the practice of teams intentionally infringing and giving away penalties when defending inside their own 20-metre zone to concede two points rather than a potential six. Wayne Bennett and Paul McGregor have been vocal critics of that tactic, leading to calls last year for a five-minute sin bin to be re-introduced.

That is not on the table but referees have been instructed to reduce teams to 12 players for 10 minutes for repeated infringements about which they have been warned.

"I'm expecting the referees to action those warnings that they (make). If a side complies, then play on. If they don't, well I expect the referee to (take) action," Archer said. "It's just that point where the referee needs to do that."

There was a clue to the position taken by the officialdom in the pres-season, with four players sent to the sin bin during two weekends of trial matches that wound up on Sunday. There were 17 instances of players sin-binned throughout 2016, which was an increase on the previous year but will rise more if players and teams push their luck with infringements on their try lines.

While Archer's message to coaches indicates a crackdown in one area, there will be no change in the use of the sin bin when it comes to another – foul play – amid suggestions last season that the punishment should be widened and dished out for offences in that category such as tripping and reckless high tackles as well as professional fouls and ruck infringements. Then Wests Tigers hooker Robbie Farah claimed last March that "I think in general we've forgotten the sin bin".

Despite no player being sent off during the 2016 season, showing just how extreme a reportable offence needs to be to result in on-field sanction beyond a penalty, the sin bin's parameters will not be extended.

"If those repeated infringements repeatedly involve a foul play element, that doesn't prevent a referee from sin binning but generally it relates to more ruck infringements," Archer said.