Mr Bell said the use of warnings was positive but the government was "irresponsible" for not making legislative changes to reflect how the law was largely being applied in practice.
"There is a point where politicians do need to be responsible and not accept that it's okay for the police to turn a blind eye."
Inspector Clifford Paxton, area commander Western Bay of Plenty, said police took the impact of illegal drug use seriously and had noticed a significant reduction in the amount of cannabis in the region.
''But at the same time we have noticed an increase in the availability of methamphetamine,'' he said.
Mr Paxton said police had discretion regarding steps taken when low level offending was reported, including warnings, pre-charge warnings or prosecution.
However, the legislation regarding drugs was set by the Government and police powers of enforcement, including its use of discretion, were applied equally based on the facts as they are known about each matter.
Mr Paxton said people were still growing cannabis and police were continuing to find and destroy areas where cannabis was being cultivated.
A spokeswoman from the office of Police Minister Judith Collins said, as with any low level offending, police had discretion regarding the steps that could be taken when an alleged offence was disclosed.
"This can include a warning, a pre-charge warning or prosecution. The actions police take will be dictated by the particular circumstances of each matter."
Mount Maunganui GP Tony Farrell said both public and authority opinion had moved away from supporting blanket prohibition.
He said a 2010 Law Commission report on drugs recommended a number of reforms.
A number of national bodies, including the Law Commission, Treasury and Institute of Economic Research highlighted the pitfalls of prohibition and the benefits of cannabis reform.
The bodies suggested decriminalisation or legalisation would reduce harm for users and result in hundreds of millions of dollars of economic benefits annually.
Mr Bell said the Drug Foundation poll, which was undertaken by Curia Market Research, showed support for reform across all major political parties.
Nationally, 17,218 cannabis-related charges were laid in 2009. This figure has dropped each year and was 6492 last year - a drop of 62 per cent.Number of people convicted for cannabis possession
Tauranga District and Youth Courts
2009: 244
2010: 240
2011: 137
2012: 118
2013: 94
2014: 77
2015: 70
Waihi District and Youth Courts
2009: 28
2010: 24
2011: 13
2012: 19
2013: 7
2014: 8
2015: 8
- Source: Ministry of Justice