An advertisement for a dodgy birth certificate reseller is back on Google, with less than a week since the web giant said it had removed it.

Last week it was revealed the ad was the top Google result for Kiwis searching for their documents online.

The site more than doubles the price of requesting a birth certificate. By Google's own rules, that should bar it from advertising on the search engine.

After our enquiries last week Google took the ad down, saying ads that intend to mislead or deceive users violate its policies.

But the ad features at the top of the search results again.

The ad as it appeared days after Google said it had taken it down. Image / Google

Meanwhile travellers are being warned to avoid similar rule-breaking ads for visa resellers, which Google is also continuing to promote in searches.

Searching for a United States travel visa throws up a shock of ads for official-looking sites, some of which charge more than 10 times the official price of $22 for an Esta application.

Google was asked about the ads last week. A spokesperson said yesterday they were "looking into" it.

House of Travel Director Brent Thomas said while the ads persist, people need to be vigilant.

"Most people going to the States will need an Esta so obviously there's a significant number of people going onto sites to get one," Thomas said.

"We've certainly had a number of people complain to us this year."

The Google Ads campaign tool shows a typical "travel services" advertiser sets a monthly budget between $300 and $1,450.

The tool estimates the top end of that budget range could garner up to 31,800 impressions and 1,700 clicks a month.