Drink spike prosecutions have fallen to a five-year low – raising fears fiends like Reynhard Sinaga are going undetected.
Just 102 people have been taken to court since 2015 despite thousands of reports to police.
Only nine people have been charged in the last year, compared to 31 the previous year.
For years 37-year-old Sinaga, Britain’s worst rapist, drugged and assaulted Manchester victims unchecked.
In January the got life for 159 sex offences over a two-year-period, including 137 rapes of young men.
Colin Mackie of Spike Aware UK said: “We fear the case of Sinaga may just be the tip of the iceberg. Spiking seems to be on the increase.
“We have heard many stories from those that have been spiked, and a recurring theme is the fact that the police don’t seem to take reports seriously.
“We understand it is a very difficult thing to prove but police need to be more proactive in bringing perpetrators to court.”
Data from 22 out of 43 forces found there were at least 2,650 reports of drink spiking in England and Wales between 2015 and 2019.
Five Court of Appeal judges are due to decide this week if Sinaga should be locked up for the rest of his life after his 30-year minimum jail term was branded “unduly lenient” by the Attorney General.
One of Sinaga’s victims urged anyone who thinks they have been spiked to report it. He said: “If they’ve done it to you they may have done it before or do it again. I know from what happened to me that the police take it seriously.”