Google has gone radio silent after re-instating a dodgy ad which has caught out hundreds of New Zealanders.

The ad is for an offshore birth certificate reseller which charges kiwis twice the official government price to request documents.

Google last week took the ad down, saying it violated its own policies, but just days later the search engine is again taking the reseller's money in exchange for a spot at the top of the search results.

Netsafe CEO Martin Cocker says the company needs to be more vigilant.

"Consumers should expect a platform to follow its own rules and the next expectation is those rules would be in line with major trading practices, and certainly we should be able to go online and from the major players expect those things to be in place."

He says internet users deserve better from the web giant.

"Where there are categories in advertising which are being constantly exploited, the expectation those would be monitored and properly looked after, but in general terms we have a high volume of businesses which have an excuse for not following your own rules."

• Rule-breaking birth certificate ad back on Google within days