The NRL has strengthened its regulations on betting, forcing bookmakers to be in an agreement with the league and banning most exotic options.

As part of a bid to eliminate the possible manipulation of results, the league emailed bookmakers in December to put stringent new rules in place.

Included was the scrapping of a number of novelty options, including head-to-head player bets, most runs, most metres and most tackles, a NRL spokesman confirmed to AAP.

Betting on the number of 40-20s kicked in matches has also been outlawed, along with wagers placed on under-20s matches and the team-to-trail option.

Bookmakers will also need to enter into an arrangement with the NRL before they are allowed to offer any options on matches.

The spokesman stressed the email was sent well before the latest allegations against Wests Tigers centre Tim Simona emerged.

Simona is due to provide his answers this week to the league’s allegations of breaching rules relating to gambling on NRL matches. The case against him was handed to Simona on Friday.

It has since been reported he had placed bets on players he had been marking to be the first try-scorer in that game.

It is the latest betting scandal to hit the league in what has been a controversial 12 months for the sport and its bookies.

A NSW Police strike force was launched last year, investigating claims that up to three games had potentially been manipulated in the past two seasons.

Those matches are understood to be separate to the Simona claims.

NRL chief executive Todd Greenberg warned last week that any players found guilty of betting on matches could face a life ban.