Online music videos are to get age ratings to help protect children from highly sexual and violent content, David Cameron has said.
The Prime Minister unveiled a pilot scheme involving YouTube and Vevo as he gave details of his own struggle to prevent his son and two daughters watching inappropriate material.
Concerns have been growing for years about the kind of footage freely available to young children online. Examples of videos that have caused alarm include Miley Cyrus's Wrecking Ball, which shows her suggestively licking a sledgehammer, and sexual images in Robin Thicke's Blurred Lines.
Under the arrangements being tested from October, record labels will submit videos thought likely to attract a 12 rating or above to the British Board of Film Classification (BBFC).
Sites such as YouTube will then display the ratings, and they could potentially be used by filtering software to enable parents to block unsuitable clips.
Delivering a speech in central London this morning, Mr Cameron said he was determined to give parents tools so they can raise their children effectively.
"To take just one example - bringing up children in an internet age, you are endlessly worried about what they are going to find online," he said.
"So we've taken a big stand on protecting our children online. We're making family friendly filters the default setting for all new online customers and we're forcing existing customers to make an active choice about whether to install them.
"And today we're going even further. From October, we're going to help parents protect their children from some of the graphic content in online music videos by working with the British Board of Film Classification, Vevo and YouTube to pilot the age rating of these videos."
He added: "In as far as possible we should try to make sure that the rules that exist offline should exist online.
"So if you want to go and buy a music video offline there are age restrictions on it. We should try to recreate that system on the internet."
Asked about his own experiences with Nancy, 10, Elwen, eight, and three-year-old Florence, the premier said: "As for my own children, I am sure there are times when they have been disappointed because they haven't been able to do something or see something.
"But that is part of what being a parent is about, is being able to deploy the use of the word 'no' and even sometimes to deploy the use of the off switch on the television, as unpopular as that might be - and sometimes ineffectual because they find another screen somewhere that is switched on."
The pilot scheme will start to bring online music videos into line with those sold on DVD and other physical media - which will be obliged to have age ratings from October under the Video Recordings Act.
The BPI, which represents the recorded music industry in the UK, said: "We agree with government that, with so many more music videos now being released online through such sites as YouTube and Vevo, it is important this content is made available to the public in a responsible way, that is sensitive to the needs and concerns of younger viewers and their parents in particular.
"The BPI and its members are therefore working with the BBFC, digital service providers (DSPs) and with the support of government on a pilot scheme that will trial age ratings for music videos released online through the UK.
"Technical details are still being developed but the scheme will see UK record labels voluntarily submit content likely to be rated 12 or above to the BBFC for classification into 12, 15 or 18 age categories.
"Labels will then include this data with a 'parental advisory'-style alert in its feed to the digital service providers so that users, including parents, can make a more informed viewing decision.
"The pilot will commence on October 1, coinciding with changes to the Video Recordings Act that will require physical music videos deemed to include 12 rated-plus material to go through the same age classification process.
"The pilot is expected to run for at least three months, followed by a period of evaluation to assess the voluntary scheme.
"If, as hoped, the pilot proves successful, then as a key next step we would call on digital service providers to introduce filters linked to those age ratings so that families have the additional option to block video content they consider unsuitable viewing for children."
Mr Cameron made the announcement as he pledged to put strengthening families at the heart of everything the Government does.
The drive will see the impact on families made a standard element of Whitehall's assessments for new policies.
Funding for relationship counselling through Relate is also being doubled to nearly £20 million.
Delivering a speech in central London, Mr Cameron said politicians were often nervous of talking about relationships because they did not want to appear judgmental.
"I know that I am far from the perfect father and husband, and I will never pretend otherwise," he said.
But the Premier insisted the issue was too important for government to ignore.
He said he was "proud" that the coalition was recognising marriage in the tax system, and had taken action to ensure people of all sexualities could wed.
Mr Cameron also revealed that he had asked the Home Office to look at another reform to marriage - so that the mother's details are recorded on registers rather than just the father's.
Shadow education secretary Tristram Hunt said: "David Cameron's fictitious family-friendly agenda won't fool anyone.
"David Cameron's Government will have taken away up to £15 billion in support for children and families by 2015, while childcare costs are up and there are 628 fewer Sure Start children's centres across the country.
"It's a bit rich for the Prime Minister to offer warm words when hard-working families are suffering. Working parents are worse off and thousands have been hit by the bedroom tax. The Government has let families down by standing up for just a privileged few."