The government is currently compiling a list of websites that face being blocked by new filters, which it asked ISPs to introduce last year in an attempt to block porn sites by default.
Since prime minister David Cameron announced the online safety measures in July last year – in a bid to protect children against viewing inappropriate content – a number of charities that aim to educate children about health, sex education and drugs issues face being blocked.
The whitelist will be used to ensure such websites are not immediately blocked, according to the BBC.
The list is being compiled by a policy working group, which is also looking at ways to set up a standard system that will let any site which thinks it is being wrongly blocked tell ISPs about the mistake.
“Research suggests the amount of inadvertent blocking is low,” David Miles, chair of the working group, told the BBC.
“However, if you are a charity and you deal with teenagers in distress that one or 10 matters to you.”
The group has been meeting with ISPs, charities, representatives from government, the British Board of Film Classification and mobile operators since December.
“We are building a master list of sites that the charities are helping us with and actively testing this right now,” Miles added.
The list will be shared with ISPs to ensure that the educational sites become widely viewable.
A spokesman for the Internet Service Provides Association said: "There's a growing realisation that filters are not perfect and will lead to some over-blocking,"
"There's a feeling that some sites sit in a grey area and more needs to be done for them."