The prime minister should summon his relevant ministers and decide not to proceed with Heathrow’s third runway. As protesters were festooning the Palace of Westminster with banners on Wednesday, Gordon Brown rightly told the Commons that decisions on such matters should be taken in the house and not on its roof.

But he knows that the House of Commons does not take decisions; the government does. His government has acquired a dreadful reputation for not taking them or fudging them or reversing them or just umming and ahing. Now he has an opportunity to bang the table and say, no runway.

Last autumn Ruth Kelly, his new transport secretary, felt the full heat of commercial lobbying as BAA, the London airport operator, and BA, Britain’s flag carrier, told the government to break its historic pledge to the people of west London “for all time” that there would be no new runway at Heathrow.

As recently as 2001 they had agreed that a new runway was “totally unacceptable”, but this was a tactic to secure permission for terminal 5. It was blatant corporate mendacity, like BA’s claim that a third runway would reduce carbon emissions. Now they claim to want a terminal 6 and a fourth runway. Will they, we wonder, be content to leave the Queen safe in Windsor Castle?

The government, having allowed yet another giant travel warehouse to be built at terminal 5, has been thrown into a total dither. Its business friends told it that it should agree to the runway but it could not face saying so. Ministers first suggested a smaller runway, then a bigger one. They did what Brown always does when reluctant to decide and “went out to consultation”. This is a signal to interested parties to spend money like water on public relations to ease any eventual ministerial pain.

The result was apparently unforeseen, a deluge of 18,000 objections, a direct action campaign and sustained abuse of ministers for what, with every passing month, seems a dumb, not to mention antediluvian, retreat before the Big Carbon lobby.

The Civil Aviation Authority unhelpfully published a map of the noise zones for landings and takeoffs for jets using the new runway, apparently embracing everywhere with a W in its postcode, not least Hampstead, Kensington and Chiswick. It also published a new set of stacking patterns over the London area. Some seemed craftily located plumb over outer London marginal constituencies.

London’s airport planning has yet to arrive in the 20th century, let alone the 21st. Short of converting jumbo jets to gliders, the present pandemonium in the sky over Richmond and Windsor is to be extended to much of west London. Such has been the deluge of protest that ministerial faces are said to blanch, despite a countervailing burst of the most frantic wining, dining, job-offering and expenses-paying campaign known to Whitehall lobbying.

The biggest chicken now coming home to roost at Heathrow is the failure, in the 1970s, to locate London’s third airport on Maplin Sands in the Thames estuary, as recommended by all pundits apart from those interested in seabirds. Instead it was put at Stansted, which the airlines hated and where every countryside lobby would fight future growth. The same was true of Gatwick, whose residents were given a similar pledge to Heathrow’s but in their case one that has been honoured, so far.

The pressure duly reverted to Heathrow. Surrounded by dense development and with landings and takeoffs being over residential neighbourhoods, this must be the craziest place in Europe to site a large modern airport. That Heathrow still has only two runways, when most international hubs have at least three, is testament to the stupidity of allowing Heathrow to expand at all.

The predictable has happened. Heathrow became the “flag carrier” hub of British aviation and its relentless growth a test of government machismo. While expanding Gatwick and Stansted would have affected fewer people, they were not where BAA and BA wanted to be. Money talked.

The disastrous privatisation of BAA as a de facto monopoly saw it slide into the hands of the Spanish giant Ferrovial. This is one of many European corporations able to use its domestic security to stage highly geared takeover bids of British quasi-monopolies, bids that would not be tolerated by any other European state. It bought BAA two years ago for £10.1 billion, saddling the company in the process with a colossal £9.3 billion of debt. Sceptics wondered how this could possibly be serviced.

Handling this debt has dominated BAA management ever since, as Heathrow’s users have witnessed to their horror. An inability to handle lunatic decisions on airline security has left queues everywhere. Each last penny has been squeezed out of the company, so that the airports look like downmarket shopping malls with retail outlets cramming every corner, while delayed passengers sleep miserably on the floors. One reason BA is slithering down the airline performance league table is its deathly embrace with BAA.

In desperation BAA is selling both its property arm and its retail business, World Duty Free. There are persistent rumours in the City that it may be forced to stop all airport maintenance and terminal renewal – right before the London Olympics. Its debt is threatened with junk status, making it highly expensive to service. This is what happens with dumb privatisations. Last week push came to shove and Stephen Nelson, the BAA chief executive, was fired after less than two years in the job.

BAA may say it needs a third runway but this conforms to no known canon of planning, except possibly that of concentrating all the miseries of modern transport where they already exist. While the relative carbon footprint of air travel is often overstated by lobbyists, it must be mad to plan to allow such travel to double over the next two decades with no attempt to curb demand with higher taxes.

Business may like good air links, and having London as a European hub may have beneficial side effects (for some), but the atrocious state of Heathrow does not appear to have impeded London’s advance over the past decade. And it defies common sense to confuse the market for commercial travel with a separate, carbon-crazy boom in cut-price foreign holidays that cannot be considered a national economic necessity.

Only a third of travellers using Heathrow are classified as business, and even fewer of London airports overall. The claim that Heathrow expansion is “vital” for British business is palpable rubbish. The fiscal indulgence of the cheap travel market by the Treasury over the past decade has been a political indulgence, in effect buying votes.

The solution to Heathrow’s manifest problems would be to expel to other airports all destinations that can as quickly be reached by train, all that are primarily for leisure and all private jets. A lot of prestige national airlines might be upset, and a few tycoons. But travel is always a balance of inconveniences. If Heathrow is facing a crisis, then curb the monster; do not just feed it.

Most normal people are now persuaded that, whatever else should guide planning policy, a concern to reduce waste and conserve energy should be uppermost. It would be appropriate to use the tax system to reduce Britain’s carbon-heavy holidays. It would make sense to boost domestic tourism by discouraging foreign travel. Britain is heavily in the red on its tourism account. It would also make sense not to build another airport anywhere in London but direct traffic, whether it likes it or not, to regional and local airports and reduce pressure on the roads.

The truth is that on a fiscally level field, we have no knowledge of what might be the demand for air travel, as against a propensity to take more holidays at home. Either way the question deserves consideration. Or do Brown and Kelly have absolutely no commitment to joined-up government?

Sometimes a prime minister must lead rather than follow. Sometimes he must go in unpopular directions. Yet one of the achievements of the green movement has been to make its concerns both global and popular. That popularity should help this ever timid prime minister to reject the third runway and get his air travel policy into some sort of order.

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