Free countries should be fractious places. Newspapers, television channels, magazines, electronic information services are there to amplify the arguments - in short, to cause more trouble. This newspaper was founded precisely because the great media warlords of print and screen cause too little trouble in the bear garden of ideas.

Stephen Dorrell's proposals to overhaul the rules governing how newspaper and television companies can own shares of the each other's markets suggest that the Government takes seriously the need for more trouble. It has recognised that the present system isn't delivering sufficient competition and that it is needlessly complex and arbitrary. To move towards a system which assesses competition policy across the whole media market, rather than within its subdivisions of print and broadcasting, must be sensible. Confining the large players at roughly their present shares, while encouraging smaller firms to grow across several different media, also feels right. Mr Dorrell's new simpler thresholds for market share should be workable.

Strangely the BBC has been left alone, on the grounds that government already, in a sense, oversees it. That a state-owned dominant player should be thought less threatening to competition than a private one is a conceit rich in irony and one that will not last for ever.

Most important, though, ministers must now keep their nerve. At the weekend Rupert Murdoch openly defied the Government to enforce any set of thresholds. His tired and emotional reaction to the proposals yesterday merits no sympathy. Mr Dorrell should ignore him.

Mr Dorrell must also decide soon who the main media competition troubleshooter will be and what powers he or she will have. There is logic in empowering a single regulator, but the crucial thing is that the relevant authority must be able to act quickly, effectively and transparently.

The immediate verdict on the whitish-green paper is therefore broadly positive, but if we are to avoid problems in the medium term the Government will have to be still bolder. It does not seem from yesterday's announcement that it has learnt sufficiently from its previous regulatory efforts about the need to keep ahead of media technology. Mr Murdoch stole a march in setting up what is now BSkyB precisely because the 1990 Broadcasting Act left the upper atmosphere outside the ownership rules. Such loopholes can be fatal for competition. Mr Dorrell's paper has bought its ticket for the new world in which multimedia blur the boundaries between text, sound and moving picture - but it hasn't actually gone to the show.

The central problem of defining these new media markets, and developing relevant ways of measuring the share of particular firms in them, has been shelved - probably for a future government to deal with. This is an understandable reaction to complexity, but it ignores the fact that media technology moves more rapidly than parliamentary draughtsmen. If Mr Murdoch flutters his eyelashes at Microsoft's Bill Gates and their affair gives birth to a global on-line multimedia information service, the regulator (and the public) will face yet another media baron fait accompli.

Only if the Government tackles this subject is there a realistic chance that the next Broadcasting Act will have a longer life than its unhappy predecessor, which was obsolete within three years of its passage through parliament.