David Newell, director of the Newspaper Society, said that, however innocuous sounding such a move might be, it would affect everyone's freedom of expression.
He urged ministers not to respond disproportionately to what he said were the bad practices of less than 1% of journalists.
His comments come ahead of the expected publication later this month of Lord Justice Leveson's report into press ethics, ordered in the wake of the phone hacking scandal.
In his findings, he is expected to recommend greater regulation of the press.
Deputy Prime Minister Nick Clegg has already called for the Coalition Government to fully implement the proposals, as long as they were proportionate.
But critics have warned that the effect could be to muzzle the press.
In an article on the issue, Mr Newell said the focus of the Leveson Inquiry had been on "substantially less than 1%" of newspapers and magazines and the journalists that work for them.
He warned advocates of press controls showed scant interest in the impact any legal changes would have on most publications and reporters and the vital roles which they perform.
He said: "Their sense of responsibility and public value are in danger of being taken for granted with the real danger of 'mass punishment' being inflicted on them because of the behaviour of less than 1%."
Mr Newell said it had not been demonstrated more legislation was necessary on top of existing civil and criminal laws and he warned of the damage that could be done by bringing in statutory regulation.
He added: "However softly focused, or innocuous sounding, a statute-based media standards body would impact on everyone's freedom of expression and everyone's freedom to enjoy the words and images which result from that freedom.
"It would require a line to be redrawn by Parliament which would increase the range of media platforms which operate under state-supervised freedom of expression".
He also warned such a move would place Parliament in charge of regulating some media organisations but not others, such as websites.
Mr Newell said: "Put simply, the freedom to publish in the UK is rightly exercised by all sorts of individuals and organisations for a myriad of motivations and all having a choice as to their mode of publication.
"This helps guarantee wider democratic freedoms.
"To target for inclusion in a special statutory regime all those that exercise those freedoms purely on the basis that they have chosen to do so on newsprint or magazine grade paper cannot be justified on any fair evaluation of the evidence presented to Leveson."
Other suggestions to improve press standards included having a member of staff take a minute of editorial conferences and other meetings.
There have been reports that David Cameron could face a Cabinet revolt over the issue if Lord Justice Leveson's report backs statutory regulation.
Last year, Michael Gove, the Conservative Education Secretary, warned the then ongoing inquiry was having a "chilling effect" on press freedom.
In recent days observers have suggested the ongoing allegations against Jimmy Saville, which were first brought to public attention by the press and broadcasters, demonstrate the need for a press free from stringent regulation.
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