The scum-removal rating was given by measuring light reflection before and after scrubbing.
Malcolm Rands, founder and chief executive of ecostore, said the "great" results supported changing perceptions about eco-friendly products.
"There's a lot of prejudice from the past that eco products cost too much and don't really work and we are right up against that," he said.
"But now lots of companies are looking at plant-based chemicals and there is some fantastic research coming out and we are being looked to as a world leader."
He said the 4.5-star rated cleaner used just three ingredients, compared to more than 20 in some of the competing products.
Other cleaning-product firms the Herald contacted did not respond to queries by press time last night.
As well as the three top-rated cleaners, five sprays and two wipes were worth considering, according to Consumer NZ.
They were Ajax Professional Ultra Bathroom; Home Brand Bath & Shower Cleaner; Mr Muscle Shower Clean; Mr Muscle 5 in 1 Total Bathroom; Sparkle for Showers; Dettol Scrub 'n' Wipe Citrus Wipes, and Viva Shower Fast Wipes.
Overall, bleach products were discouraged.
"Bleach isn't the best way to get rid of mould, which feeds off soap scum, because it can discolour mould at lower bleach concentrations. So you think it's done the job when it hasn't," the report said.
As well as commercial products, a mix of baking soda sprinkled on to soap-scum and then sprayed with undiluted vinegar was given a 3-star rating - the same score as three cleaners.
"This is probably all that's needed to keep most bathrooms clean. Plus there's the added benefit that vinegar kills mould and its spores."
