Has the Left stopped thinking? This was the question a group of speakers, including your columnist, was invited to debate at Canary Wharf on Wednesday, at Reuters. The global news-gathering organisation is one of the sponsors of the annual Orwell Prize for political writing, and the judges were announcing their shortlists for 2008.

World stock prices, electronically displayed, chased each other around the 100-metre strap girdling the building. Into this capitalist lair the speakers from the Left had come to defend their thinking. The defence did not cohere. Few who attended the debate could have departed with a stirring case for the politics of the Left ringing in their ears. The shade of George Orwell will have heard the trumpet give a most uncertain sound.

Citing the achievements of a Labour government, one speaker began with firework safety legislation. Another mentioned the Jubilee line on the London Underground, on which he had arrived (but which was in fact built by the Tories). There was talk about the “Third Sector” and the prospects of farming out the State's social duties to little platoons of mums and charities and grassroots community organisations. A once-great political idea was disintegrating into a welter of crèche initiatives and well-intentioned wittering about small-picture communitarianism and self-help groups in Glasgow.

This is not what Marx, Engels, Lenin or even Attlee were all about. Nor, for that matter, is it what Disraeli, Salisbury, Churchill or even Thatcher were about. And I think I diagnosed the problem: a problem for the Right too, and for British Tories as much as for new Labour. All sides have suffered a slow but disabling collapse of confidence in the ability of central government to do things, to mend things, to start things or to run things properly. Nobody seems to believe in the State any more.

I do. My message to the Left is keep the faith, baby. My message to the Right is beware the siren calls of laissez faire and localism. People need governing. People need governments, strong governments. People need certainty. People need consistency. People need constraining, inspiring, harnessing and directing, and they need it done with the clarity and command that central government alone can offer. In a thousand places, from the strategic heights to the nooks and crannies of everyday life, there arise necessities to which the answer must be that only government can do this.

Only government could have put Canary Wharf itself on to the map. A Conservative government, as it happens, in which a presiding genius was Michael Heseltine. Contrary to the instincts of some in his party, and sometimes Margaret Thatcher herself, Mr Heseltine believed in intervention. “I'll intervene,” he told a Tory conference 16 years ago as President of the Board of Trade, “before breakfast, before lunch, before tea and before dinner. And I'll get up the next morning and I'll start all over again.”

Only government now can get Crossrail built to link Canary Wharf properly into an east-west route across the metropolis, and end the daily misery of hundreds of thousands of Central Line commuters in London. Private industry may do the actual construction of mass-transit public transport links, but government alone can knock heads together to initiate. The same is true of roads.

Only government can get decent healthcare for those who are poor and chronically sick. Government may hire the private sector to deliver it, but the private sector, alone and unrewarded, will not choose such business. Only government can underwrite and arrange free and universal schooling for children - by whatever mechanism, public or private, it is provided.

Only government can protect us abroad, and police us at home. Only governments can force the pace on climate change. Only government can frame, amend and administer the law. Only government, and its legislation, can defend the interests of the generality against the appetites of individuals: who but government can create a national park, guarantee a green belt, or hold back the march of a million breeze-block bungalows across the countryside?

From this great argument, the dispute about central versus local decision-making is but a sideshow, and it would be intellectually dishonest of any of our three main parties to pretend that decentralisation could be a central plank of any manifesto worthy of the name. Nobody seriously thinks all administration can be run from Whitehall, and nobody seriously thinks local government could run everything. The balance may be shifted a little this way or that but always remembering that localities and communities - cities, towns, neighbourhoods, villages and parishes - have selfish interests of their own to advance, often in competition with the general good; and there are huge disparities of wealth and power between them. Only government can settle these.

Only government can apply a framework of standards, rights, benefits and duties consistently across the country, regardless of postal code. My fellow commentator Simon Jenkins is quite wrong to hold up the achievements of 19th-century Birmingham or Manchester as exemplars of the benefits of decentralisation. England's great cities and boroughs gathered power from a confused miscellany of smaller institutions and individuals, focused it and gave it muscle for the general good. They make the case for, not against, centralisation. What Birmingham built from a score of smaller power centres Britain can build from a score of Birminghams.

Finally, only government can redistribute wealth and power among citizens. Nobody believes in absolute equality, and nobody believes in removing all help from the weakest. A balance between these extremes must be struck; where and how you strike that balance is the oldest and biggest question of all in politics - eternal, pivotal, absolutely central - and only government can strike it.

When I was young the household gods of my developing political philosophy, men such as Friedrich Hayek, Alfred Sherman and Keith Joseph, were in many ways anti-state; and to push back the demands of the State then was a noble cause. But look at the great challenges as they appear in spring 2008: the environment, national and global; the regulation of banking; fair trade; malaria and HIV-Aids; congestion; immigration; asylum ...what has anti-statism to say about any of this? I cannot remember a time when the ideas of Hayek, Joseph, Sherman et al seemed more distant to the anxieties of the hour.

The market must be the engine of our economics and therefore our politics. That argument is over. But now another starts. What about the accelerator, the brakes, the gearing, the emissions control? Left, Right, or elsewhere, this must be your province. And at its centre stands, and must always stand, government: the potential for good or ill, wisdom or folly, of the State.

Governments can do great things. Governments can do good. Keep the faith, Mr Orwell.

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