Google has been urged by a government adviser to do more to restrict access to child abuse images, after paedophile Mark Bridger was jailed for life for the murder of April Jones.

John Carr, a government adviser on child internet safety, said making it more difficult to access hardcore pornography sites, which were often the gateway to illegal child abuse images, would prevent many men accessing such material.

He said he would be urging Google to take measures in a meeting with the company next week.

Carr's remarks come after the sentencing of Bridger, who murdered the five-year-old in a sexually-motivated attack after looking at pictures of child abuse online.

Speaking to BBC Radio 4's Today programme on Friday, Carr acknowledged that Google, like all search engines, blocked access to websites they knew contained images of child abuse. "That is them being reactive, they can and should be proactive," he said.

Currently there are three safety settings on Google, which can be adjusted by the user. Carr argued that Google should turn on its "safe search" function by default, and block access to hardcore pornography sites. "They are one of the key routes that guys get to child pornography in the first place," he said.

If users wanted to change their settings to access hardcore pornography sites, they would have to register with Google and would have to verify that they were 18, Carr said. "That would be a huge deterrent for many of these guys that would stop them from getting on the pathway that lead to the child abuse images.

"Putting any types of barriers to things like that would in my opinion, and the opinion of many others, help reduce the numbers of guys who got involved with this stuff in the first place, and that would be a big step forward."

He called on Google to show moral leadership on the issue. "They are the biggest player in this space in the world. If they did it then others would follow … If Google did it everyone would have to do it."

Google has said it is committed to ending access to illegal internet sites. The company was "unable or unwilling to do an interview" on Today, according to presenter Sarah Montague.