Those instructions from an NRL coach as his players practised defending on their own line should dispel any doubt that teams deliberately concede penalties when the opposition is within try-scoring range.

With the cynical ploy now threatening to ruin matches, as it did with Thursday night's Bulldogs-Rabbitohs game, there are growing calls for a five-minute sin bin, and this column has been told referees would prefer to have that option available to them.

Some even propose the sin-binned player return to the field earlier if the opposition scores a try within the five-minute period, as happens in America's National Hockey League.

While coaches and players deny they intentionally give away penalties when under pressure near their own try line, the scene mentioned above, from a training session earlier this year, suggests otherwise.

After practising marker defence with large exercise balls in other parts of the field, the players were told to stand on their own try line.

Once in position, the head coach began repeatedly calling "cheat, cheat, cheat" as players moved more to the side of the ball rather than standing directly behind it as they are supposed to when an opponent is playing the ball.

The message was clear: do whatever you have to to stop the opposition scoring, and it has been obvious in recent games that few teams have any concern about giving away a penalty near their own line.

They do so knowing referees are reluctant to use the sin bin because of the impact that reducing one side to 12 players for 10 minutes can have on a match.

That was obvious on Friday night when St George Illawarra scored two tries after Brisbane's Matt Gillett was incorrectly sin binned, and a third just after he returned to the field.

Some within the refereeing ranks, or recently involved in officiating, say the whistleblowers are concerned about the reaction of coaches, such as Canterbury's Des Hasler, who approached the ground manager after Thursday night's 21-14 loss to South Sydney wanting to speak to NRL referees boss Tony Archer.

NRL officials say Hasler spoke to NRL referees coach Russell Smith, as Archer was not at the game, and described the conversation as "respectful".

Hasler was unhappy with a 10-6 penalty count against his team, but five of those penalties were for ruck infringements near their try line that led to referee Gerard Sutton warning Bulldogs skipper Michael Ennis late in the first half and again just after half-time that he would sin bin a Canterbury player.

Souths also conceded back-to-back penalties near their own line in the second half.

"They do it because they get a set restart and the top teams back their defence, but it is hard for a referee because 10 minutes is a long time for a team to be a man down, especially at the back end of a half," one former leading referee said.

"Unfortunately, I think referees are lacking a bit of confidence to make those big decisions, but I think the referees would support a five-minute sin bin for those repeated infringements on the try line.

"You know that if you put a player in the bin the other team will probably score, but five minutes is only three sets of tackles, whereas 10 minutes is a quarter of one half of a game."

Another experienced match official said: "It is a shame that we don't have a five-minute sin bin because I know that the referees would feel a lot more comfortable about sending a player to the sin bin for that amount of time rather than 10 minutes".

Gold Coast coach Neil Henry and former players Alan Tongue, Michael Crocker and Mark Geyer are among those to have publicly backed calls for a five-minute sin bin this season, while US-based journalist and former referee Ben Everill has suggested the NRL adopt the NHL system, which allows a sin-binned player to return as soon as the opposition scores.

"The NHL has a two-minute sin bin and a five-minute sin bin, depending on the seriousness of the offence committed, but it doesn't matter what it is, if the other team scores, the player is back on," Everill said. "To me, that is fairer. If a team scores a try in the time you are down a man then you have been penalised enough.

"Then you will find referees aren't afraid to use it and teams will stop giving away deliberate penalties if they know a player is going to be sin binned. It also brings in the possibility of using the sin bin for everything – if it is three piddly little high tackles or the team has done three crushers, then someone goes to the bin. You can stamp out everything that is a problem in the game with that."