The footballer at the centre of a gagging order over a relationship with reality TV star Imogen Thomas was named by an MP in the Commons today as Ryan Giggs.
Liberal Democrat MP John Hemming, who has been campaigning on the issue, said: "With about 75,000 people having named Ryan Giggs on Twitter, it is obviously impracticable to imprison them all."
The MP's action finally lifted the blackout on mainstream media identifying the Manchester United star even though a High Court judge had again refused to lift the injunction earlier today.
House of Commons speaker John Bercow took the MP to task over his action, saying: "Let me just say to the honourable gentleman, I know he's already done it, but occasions such as this are occasions for raising the issues of principle involved, not seeking to flout for whatever purpose.
"If the honourable gentleman wants to finish his question in an orderly way he can do so."
Mr Hemming said: "The question is what the Government's view is on an enforceability of a law that clearly doesn't have public consent."
Attorney General Dominic Grieve said: "It is our duty as parliamentarians to uphold the rule of law."
Asked whether the press would be covered by privilege if they were reporting on the exchanges that took place, Mr Bercow said: "The answer to that is yes."
Earlier, asked whether the Prime Minister thought Mr Hemming was wrong to use parliamentary privilege to name the footballer at the centre of the row, David Cameron's official spokesman said: "I don't think it is for the Government to comment on individual cases."
The spokesman told reporters that Mr Cameron had written to the chairman of the Commons Justice Committee, Sir Alan Beith, and the chairman of the Commons Culture, Media and Sport Committee, John Whittingdale, asking them to convene a joint committee of both houses to consider the issues of privacy and the use of injunctions.
The committee will be able to ask relevant figures from Government, the media and the law to give evidence, though it is not expected to be able to compel them to appear.
If necessary, the committee could hold hearings behind closed doors to avoid revealing information covered by injunctions.
It is hoped it will report by the autumn, though it will be for the committee to determine its own timeframe.
Minutes before Mr Hemming's comments in the Commons, the High Court refused to lift the ban on journalists naming the married footballer who allegedly had a relationship with Ms Thomas.
Lawyers for The Sun asked for the controversial privacy ruling to be lifted after a Scottish newspaper named the star at the weekend and Mr Cameron told breakfast television viewers he knew his identity "like everybody else".
Banning newspapers from naming such stars while the information was widely available on the internet was both "unsustainable" and "unfair", Mr Cameron told ITV1's Daybreak.
But Mr Justice Eady rejected a fresh application by News Group Newspapers to discharge the privacy injunction relating to Giggs, referred to in court as CTB, on the basis that to continue it would be "futile", given recent widespread publicity about his identity.
The judge said: "The court's duty remains to try and protect the claimant, and particularly his family, from intrusion and harassment so long as it can."
Last week, Mr Hemming said a review by senior judges of the use of injunctions was an "attempt to gag the media in discussing the proceedings in parliament" and was "a retrograde step".
But the judges insisted they were only following the laws as set down by Parliament, which was aware of the consequences of the Human Rights Act 1998 and the European Convention on Human Rights.
Mr Cameron said: "It is rather unsustainable, this situation, where newspapers can't print something that clearly everybody else is talking about, but there's a difficulty here because the law is the law and the judges must interpret what the law is.
"What I've said in the past is, the danger is that judgments are effectively writing a new law, which is what Parliament is meant to do."
The Sun newspaper challenged the order, saying "it is time for the courts to do the right thing and end a situation where readers of some newspapers but not others are allowed to know the worst-kept secret in the country".
Last week, a gagging order obtained by former Royal Bank of Scotland chief Sir Fred Goodwin was partially lifted by the High Court after allegations that he had an affair were made public by Liberal Democrat peer Lord Stoneham of Droxford in the House of Lords.
But Lord Neuberger, the Master of the Rolls and the most senior civil judge, said on Friday that the law surrounding reports of comments which intentionally contravene court orders was "astonishingly unclear".
Addressing the media at the Royal Courts of Justice in central London on Friday, Lord Chief Justice Lord Judge said: "It is, of course, wonderful for you if a Member of Parliament stands up in Parliament and says something which, in effect, means an order of the court on anonymity is breached.
"But you do need to think, do you not, whether it's a very good idea for our law-makers to be flouting a court order just because they disagree with a court order or, for that matter, because they disagree with the law of privacy which Parliament has created.
"It's a very serious issue in my view."
The Sunday Herald newspaper in Scotland published a thinly-concealed front page photograph of the player yesterday, printing his face with his eyes blacked out and the word "censored" written over the top.
Beneath the picture it wrote: "Everyone knows this is the footballer accused of using the courts to keep allegations of a sexual affair secret."
In an editorial, the Sunday Herald - the first mainstream publication to apparently identify the player - also said it was "unsustainable" for newspapers not to be able to print information which is available on the internet.
Mr Grieve confirmed he was aware of the report, but said he has not received any complaints or referrals from any parties or by any court.
There was no immediate comment tonight from Manchester United.
Giggs is due at open training tomorrow ahead of United's Champion's League final against Barcelona at Wembley on Saturday night. He is also expected at a Gary Neville testimonial tomorrow night at Old Trafford.
Mr Hemming later explained that he had decided to name Giggs to prevent people being jailed for gossiping about him.
The Birmingham Yardley MP told BBC Radio 4's PM programme: "When he sued Twitter and showed he was going to to go after relatively ordinary people and try to prosecute them for gossiping about him on a matter of trivia, I think he has to be held to account for that.
"I worry greatly about this country's willingness to lock people up in secret. I really don't think we should allow a situation where people are prosecuted and potentially jailed for two years and it all happens in secret and you can't know what's going on.
"If there is oppression going on, we should be willing to speak out about it, if you are jailing people for gossip."
Mr Hemming added: "Is it really good to have a society in which rich people use their money to persecute people of relatively ordinary means, and nobody is willing to say anything about it? I think that would be very wrong, it would be very sad."
He said he accepted the need to respect court orders "under normal circumstances" but added: "There comes a point at which it has gone too far and we are at that point."