Tennis faces "very significant" integrity problems caused by the sharp increase in internet betting, an independent report concluded in its interim finding, with one investigator describing a "tsunami" of corruption at the game's lower levels.

The Interim Report of the Independent Review of Integrity said its two-year investigation had not revealed widespread corruption at the highest levels of the professional game globally, although "there is nonetheless evidence of some issues at these levels".

The review was commissioned by the sport's major bodies (the ATP, WTA, ITF and Grand Slam Board) in 2016 following a report by the BBC and BuzzFeed News that claimed 16 players ranked in the world's top 50 had been flagged to the Tennis Integrity Unit (TIU) over suspicions that matches had been thrown.

However, panel chairman Adam Lewis said: "Match fixing is unlikely at the level of grand slam. All the indicators are clear the problem is low."

Among the report's recommendations are a greater monitoring of the lower levels of the game, with one investigator saying there is a "tsunami" of problems, plus a review of appearance fees and the ranking system.

The report also called for greater education among players, the elimination of gambling sponsorships, changes to integrity rules and for the TIU to be beefed up and be truly independent.

"The integrity problems are greatest where prize money relative to costs, prospects of advancement, pubic interest and attention, and financial resources of tournaments are lowest," it said.

Tennis operates under a pyramid system with young players competing in Futures and then Challenger tournaments of increasing value under the main tour.

The panel said the advent of online betting and the sale of official live scoring data had greatly exacerbated the problem and recommended that the ITF ends its data sale agreement at $15,000 Futures events, and probably at other ones as well.

According to the report, many of the problems date back to the 2011 agreement between the ITF and data company Sportradar for the sale of live scoring data. A further agreement followed in 2015.

The panel recognised that any change in the system would financially penalise the ITF, which it said should be compensated for by the other governing authorities.

It added that there were no simple solutions but called on the sport "to address and limit the betting markets that ultimately drive, and give expression to, the problem; and to improve the systems of preventing and disrupting breaches of integrity, and for detecting and sanctioning them when they occur.

Tennis's governing bodies have committed to implementing the report's final findings after a period of consultation until the end of June. The final report will be published later this year.

Reuters