Up to six international cricket teams have been closely monitored over the past decade because of corruption concerns, according to former International Cricket Council (ICC) Anti-Corruption Unit head Paul Condon.
Condon set up the unit after the 2000 match-fixing scandal which led to life bans for international captains Hansie Cronje (South Africa), Mohammad Azharuddin (India) and Salim Malik (Pakistan).
"Since 2000 there have been probably five or six national teams who at some stage have been causing concern and have been closely monitored and scrutinised," Condon said in an interview published in the December edition of The Cricketer magazine which goes on sale this Friday.
"In terms of frequency, probably Pakistan has been the most challenging in recent years."
Former Pakistan captain Salman Butt and pace bowlers Mohammad Asif and Mohammad Amir were jailed this month for taking bribes to fix incidents in last year's Lord's test.
Condon said an explosion in Twenty20 cricket had been a major factor in the re-emergence of cricket corruption.
"Probably the greatest trigger point was the explosion of T20. The 'anything goes' party atmosphere allowed some really bad people back into the game. Some of the notorious fixers from early years started to re-emerge on the circuit in India, Pakistan, South Africa, Australia and the United Kingdom.
"It almost legitimised the bad guys being back around cricket again, and fixers were even seen in promoters' boxes and at matches. What up to then had been pretty tight and regulated, suddenly became a free-for-all."
Condon said Twenty20 cricket "took away the discipline and rigour we (the Anti-Corruption Unit} had been enforcing" and that players were exposed to "lots of people making very, very big sums of money".
"I think the temptation was to do a little fix here and a little fix there and still win the match -- and they were not seeing it as criminal," he said.
Condon said the sport was now at a critical juncture.
He said the Anti-Corruption Unit had to boost its resources to match the volume of cricket being played and also get tougher with national boards, imposing a progressive scale of punishments until they reached the "nuclear option" of excluding them from world cricket if they continued to fail to drive out corruption.
He said players had also to become involved in running the game at the world level in order to accept more responsibility.