He had become everything that is wrong with New Labour

The clarity that has evaded Stephen Byers so disastrously returned to him too late - in his resignation speech. He had, he told us, become a distraction and confessed to "many mistakes and regrets". To which, you couldn't help thinking, the national response was: "You can say that again."

Watching the last agonies of the Secretary of State for Transport has been a vivid exhibition of political collapse. The unravelling of Mr Byers has been brutal, the fall from model Blairite to icon of political unpopularity devastating. Yesterday, we watched a political suicide - perhaps subtly assisted - from someone who could see no way to go on. All that awaited was further rows, more blame and final, inevitable defeat. I do not claim to know what his nightmares were like, but they must have come as a relief after his day job.

They will miss him though, the Minister for Things That Went Wrong. Who will fill the gap as the unpopular face of the Blair government now? All politicians long to shift blame. It's the human being in them. At the nadir of his standing, Richard Nixon grumbled that "you won't have old Dickie Nixon to kick around any more", and Mr Byers has ably fulfilled that role for New Labour for some time .

But whenever people list Mr Byers's failings, as if they were somehow peculiar to him, I cannot help thinking that they are really describing the Government's wider flaws and weaknesses, conveniently embodied in one person. Looking back to my first encounter with him just after Mr Blair's election, I discover myself describing him as "very like the Prime Minister ... he has the knack of speaking with many voices without ever quite contradicting himself", and "conveniently leaving everyone with the impression that he shares their particular concern". Such characteristics were in demand when New Labour was establishing itself as unthreatening. They became liabilities. We profoundly distrust the very smoothness we once found reassuring.

How can this brutal inversion have happened? Is Mr Byers uniquely burdened with failings? Is he stupid? Did he set out to be deceitful? No - it is far worse than that. Mr Byers is a symptom of so much that has gone wrong - and is still going wrong - with New Labour. Spin and the attempted manipulation of performance are often singled out for censure. Perhaps even more worrying are the failures to implement policy quickly and clearly, followed by panic at the failure to deliver and an insistence that everything is going better than it really is. The illusions are recycled, looking a little more wan each time.

This dire recurrence befell Mr Byers early on in his ministerial career. We were at a conference together when BMW's plan to close Longbridge was made public and he suffered his first disgrace of not having appeared to know that the closure was coming - or perhaps he had and hadn't acted on it. "Yes," he said gravely. "We must learn the lessons of Longbridge." But did he really mean learn them - whatever they were? Or did he mean that he was trying out a neat alliterative sound-bite to see if it would work? There was more of this - much more, until I don't think he realised how bad it all sounded. It was like watching someone fall prey to a cocaine habit, needing more and more of the same buzzy distraction just to get them through the day.

There is no excusing his misjudgments. But if we were only to conclude that Mr Byers's weaknesses were exclusive to him, we would be missing something rather more significant. Gordon Brown's hostility to Mr Byers has been unrelenting - he regarded him as a spy from the Blairite camp from the moment Mr Byers was launched on his Cabinet career as Chief Secretary to the Treasury. Yet so many of the things that went so badly wrong for Mr Byers were masterminded by Mr Brown, because very little can happen without the prior approval of an especially mighty Chancellor. The plans for taking Railtrack into administration, the Public Private Partnership for the Tube, the selling-off of air-traffic control: all of these moves were explicitly agreed with - and in some cases demanded by - Mr Brown. So too was the initial refusal to compensate Railtrack shareholders, which deepened the Transport Secretary's unpopularity.

No Treasury minister ventures forth to defend these decisions. Indeed, I have long suspected that defending Mr Byers would have been a hanging offence in the Brown camp. He was also a foot-soldier in some particularly bloody wars in the invisible front of Government, and they will rage on without him. As for Mr Blair, he has lost a useful lightning conductor. Mr Byers grimly conceded in his farewell speech that he would be remembered as the man who kept Jo Moore in her job after the 11 September e-mail. That was a dreadful error - but one for which the Prime Minister should shoulder a share of blame since it was Number 10 which stubbornly refused to offer up Ms Moore's scalp: as he should, too, over the unwise acceptance of a donation from the newspaper tycoon Richard Desmond. Mr Byers may have been slippery on this subject, but he was, so to speak, slithering on his master's behalf.

The final act of a fatally damaged minister was symbolic: the ditching of the 10-year transport policy - a decisive move, made far too late to save him. This was Mr Byers's way of saying that the mess in transport began long before he got there. John Prescott's 10-year plan was indeed a shambles which alienated motorists, but had no compensatory prospect of ever working. Whoever succeeds him must be given the authority to start anew and the Prime Minister's strongest support to tackle a department which has become accustomed to failure.

The sad thing about Stephen Byers is that he started out as an energetic minister who meant well and wanted to do a decent job in a responsive, successful Labour government. Four years on, he was hopelessly mired in the thickets of illusion, buck-shifting and turf wars that are the darker side of the Blair years. It was high time he went - which is not the same as saying that his going will solve the malaise. Mr Byers was a living symptom of New Labour failures.

He was not their cause.