The government wants ISPs to block access to pornography websites, so web users do not need to rely on parental controls to ensure children are not exposed to inappropriate content when surfing the web.

Culture minister Ed Vaizey is to meet with ISPs including Virgin Media, TalkTalk and BT "in the near future" to discuss the plans.

Vaizey's plans, which follow moves by UK ISPs to block access to all websites containing child pornography images, also include the ability to 'opt in', which means web users will have to request access to specific sex-related sites.

"This is a very serious matter. I think it is very important that it's the ISPs that some up with solutions to protect children," Vaizey told The Sunday Times.

"I'm hoping they will get their acts together so that we don't have to legislate, but we are keeping an eye on the situation and we will have a new communications bill in the next couple of years."

A number of ISPs said implementing the scheme would be technically challenging and expensive. However, Andrew Heaney, executive director of strategy and regulation at TalkTalk, told The Sunday Times: Our objective was not to do what the politicians want but to do what is right for our customers. If other companies aren't going to do it of their own volition, then maybe they should be leant on."

Meanwhile, Virgin Media revealed it already offers an opt-in function when surfing the web from mobile phones.

"We're able to block sites, so it would be possible to do the same on the internet. It is just about finding the right approach," a spokesman said.

During a recent parliamentary debate, Claire Perry, Conservative MP for Wiltshire, called on the government to put pressure on ISPs to block pornography websites after 60 percent of nine to 19 year olds admitted they had found porn online but only 15 percent of computer-literate adults with children knew how to turn on parental controls.

See also: EU: Blocking child porn websites is insufficient