Test cricket remains at "high risk" of being targeted for corruption according to ICC chief executive David Richardson, but he believes the dangers posed to domestic and even junior-level cricket is the clear and present danger as the fallout continues from the Al Jazeera documentary on spot-fixing released last week. He also admitted that corrupt elements were here to stay and it was a "constant battle" to weed them out.

The documentary alleged that three England and two Australian players had agreed to score at a rate specified by fixers for the purposes of betting on certain 10-over periods in two Test matches in India. The two matches in question were the final Test of England's tour of India in 2016, which was played in Chennai, and the third Test of the Border-Gavaskar Trophy last year in Ranchi.

According to Richardson, the documentary revealed that the corrupt elements were reacting to the "mitigating measures" put in place by the ICC's Anti-Corruption Unit (ACU) which had disrupted the fixers with the support of the players who had started reporting approaches.

Consequently, the fixers were approaching other elements in the game including groundsmen, to doctor pitches that would suit bookies as the documentary portrayed. "Because we have hardened the target at the top level they are now going to focus on junior levels of cricket or other avenues such curators and groundsmen," Richardson said at a 2019 World Cup event in London on Wednesday. "We know what the problem is. It is going to be a constant battle. We can't let up. We'll be in it for the long term."

Richardson said despite the ACU putting all deterrents in place, including a robust education programme for players, all forms of cricket including Tests remained vulnerable. "It [Test] is as high a risk, but we've got the mitigating measures in place to make sure that it cannot have any impact," Richardson said. "And, yes, it would be very surprising if international cricketers were able to be got to. And because that target has been hardened, these guys are now trying to create their own leagues, at a much lower level, and the danger is they will start going to domestic tournaments and leagues that are televised."

Richardson said his first reaction having watched the documentary was anger that there were people who are essentially "criminals" that are "swanning around" the game to destroy its integrity. "We are obviously very much aware there are these types of individuals and types of criminal groups around world who are trying to get into cricket, trying to get hold of players, trying to get hold of groundsmen But it was reminder that these guys are at work and they are not going away and we've got our work cut out trying to disrupt them."

In its initial reaction to the documentary, the ICC said that Al Jazeera had "refused" to cooperate despite "continual requests" to share the "unedited and unseen" feed which were hampering investigations.

In the documentary, one of the persons that Al Jazeera interviewed implied that anti-corruption officials employed by the ICC were either compromised or could easily be sidestepped by fixers with money and connections.

"At this stage there is no evidence to suggest that is the case, but one of the allegations that has been made and we will look at it," Richardson said. "If your own officials, hired to do the job of protecting the integrity of cricket are compromised in any way obviously that is a concern. There is no evidence to suggest at this stage that is the case."

Both Cricket Australia and the ECB said there was no "credible evidence" linking their players to the allegations in the documentary. Although it redacted the names of the players, Al Jazeera said it would pass on information to the relevant authorities. Asked if he was aware of names, Richardson said he personally did not know their identities. "We have asked. I don't know the names of the players."

According to Richardson, ICC officials are scheduled to meet Al Jazeera over the "next couple of days" and he believed there was "no reason to think" the television network would not co-operate to carry out a thorough investigation.

"I'm sure they will work with us. After all they have stated in the programme itself that their objective is to highlight the problem and make sure the world knows about it. Hopefully that level of cooperation would be there and we will be there to get all the evidence needed to fully investigate and make sure if there has been any wrongdoing that we get to the bottom of it and deal with it appropriately."

Richardson said he would not like the judge whether Al Jazeera's sting operation was correct or not. "I think it's too early to come to those kind of conclusion. Let's investigate, let's see what they've got, what kind of evidence there is, we don't know, so I think let's leave it to the investigators to get stuck in with Al Jazeera, get to the bottom of it, and then we can decide at the end whose judgement was right, and whether Al Jazeera's judgement was right."