A new measure, which slipped almost unnoticed through Parliament in the last days before Christmas, scraps tight controls on aerial advertising and enables aircraft to be used to promote goods and services.
This latest deregulation raises concern that ministers are out to "commercialise the skies" and bring about a massive increase in using them to promote products.
MPs will call for a debate on the measure this week, and have already put down a motion condemning the move as "an unwarranted intrusion into the freedom to see the sky, which has been enjoyed as a source of tranquillity and beauty for millennia".
But the Department of Transport, which pushed it through, maintains it is merely "rationalising some very old and illogical rules".
Up to now, aircraft have been governed by strict rules on advertising, largely as a result of vigorous campaigning by conservationists in the 1930s, in the early days of flying, who insisted that the "exploitation of the skies for advertising purposes is an unwarrantable intrusion on the privacy of individuals and the rights of the community".
Only the owners or charterers of aircraft or balloons, for example, could display their names and logos on them, but now under the Civil Aviation (Aerial Advertising) Regulations, which came into force on 20 December, they can be used for any form of advertising.
It means that a major airline could sell space on the bodies of its jets to advertise Coca-Cola or McDonald's, for example.
Under the new rules, illuminated signs can now be attached to helicopters and airships, enabling advertising by night as well as by day.
Banners can be strung on the cables of kites and moored balloons, and towing banners behind aircraft will continue to be allowed.
Cynog Davis, Plaid Cymru MP for Ceredigion and Pembroke North, said yesterday that he would contact the Labour and Liberal Democrat parties this week to try to mobilise joint pressure for a debate.
"This is not what the skies are for. The Government's action commercialises them and pollutes them with advertising," he said.
"It sets a very bad precedent and opens the door to even worse development. The next thing that we will see is slogans being scrawled in the sky with vapour trails."
Neil Sinden, of the Council for the Protection of Rural England, which led the campaign against aerial advertising in the 1930s, says: "You can't get away from the sky: that is what makes it such an effective advertising medium. This measure opens the way to a great extension of the use of the skies for advertising, both by day and night."
He points out that aerial advertising would lead to more noise pollution from aircraft as well as visual intrusion.
But the Department of Transport says that the new measure "will not weaken controls" though it admits that aerial advertising is likely to increase as a result.