Mr Blair, for one, is convinced that he is still leading a government of reform

The Blairites wish to break what seems like an unholy alliance between their tormentors on the right and their critics on the left

This afternoon, Tony Blair will make a speech designed to persuade an audience of some 750 invited Labour supporters and fellow travellers that he is still leading a government of the left. He himself would almost certainly not describe his annual Fabian lecture that way. But a great many of his points, at least if he sticks to anything like the draft that was circulating yesterday, cannot logically be interpreted in any other way.

It's likely, for example, that he will make something, when he talks about public service reform, of the consequences of the Labour government's historic failure in the 1960s to see through reform of quite another kind, that of the trade unions. It was that failure to act on In Place of Strife, the late Barbara Castle's White Paper, that, he thinks, allowed Heath's government to attempt, and Thatcher's to achieve, union curbs that were much more draconian than any Wilson's government would have created if it had had the courage. The parallel he will invite sceptics to consider is that if this Government fails to reform public services, the task will be left to a government that does not believe in them and will inevitably run them down.

He will point out that even the most genuinely innovative and radical Labour government - that of 1945 - was frequently as barracked, from the left as well as the right, as his is. He has been much struck, it's said, by a 1954 New Statesman profile of Attlee that said baldly that his much revered government, which introduced the National Health Service among many other things, "contributed almost nothing new or imaginative to the pool of ideas".

He will try to rebut the persistent claims that health and education reforms are ushering in some form of two-tier provision when, he will insist, two-tier provision was exactly what this Government inherited as part of the massive "progressive deficit" that had accumulated since 1979. Haven't primary-school standards been rising faster under his own Government in poorer areas than they have in more prosperous ones?

He won't, it's safe to assume, talk any more about "equality" than he has in the past - seeking instead to focus his audience on a programme of "equity and choice". But he will point to the still huge inequities in British society, which he will depict the Government as determined to reduce.

And he will argue that the general election, two or even three years away, will be fought on quite traditional left/right lines, with an opposition that will be anti-public service investment, anti-European, anti-immigration, conservative on family and social issues and reactionary on the constitution. Know your enemy, he will imply to his overwhelmingly Labour audience, and it isn't us. Don't fall into the trap of ventilating the arguments of an opposition that sees itself as born to rule and a Labour government as a historic aberration that, in its nature, is not built to last.

It promises to be an important speech, designed to fulfil several functions. One is to persuade a once again very restive party of something that hasn't been very obvious in recent weeks, that New Labour still has a sense of purpose. Another, more incidental, will be to turn the corner, after a barrage of criticism for the reshuffle. And another, more subliminal, may be to break what sometimes seems to the Blairites an unholy alliance between their tormentors on the right, particularly in the press, and their critics on the left.

There is something real in each of these arguments. But Mr Blair will be doing a disservice to his non-Conservative critics if he doesn't acknowledge that some of their fears are real, too. The planned reforms of the judiciary and the lord chancellorship, which Mr Blair has been obliged to defend in the Commons tomorrow, are a case in point.

There is a great deal to be said in favour of these changes, provided they do what they are supposed to do and separate the appointment of judges from the clammy hand of the executive. Which is one of the reasons that - for example - the Master of Rolls, Lord Bingham, has long been in favour of them. But not, and here's the point, because modernisation of form is necessarily worth doing for its own sake and everyone who expresses doubts about is a deep-dyed reactionary. The lord chancellorship may be an anachronism, but not because its holder wears tights and his job has been around for 1,400 years.

To persuade his opponents to embrace these reforms, the Prime Minister is going to have to do two things. One is to acknowledge that, as it happens, the appointments made by the last two Lord Chancellors, Lords Mackay and Irvine, have rather reinforced an independent judiciary - indeed, one that has irritated ministers at times for rightly standing up to them in the medium of judicial review. So the arguments are going to have to be rather more profound than merely resorting to "modernisation" and saying, however admirably, that judges should: (a) be more diverse in background; and (b) shouldn't be appointed by ministers - especially as it's overwhelmingly probable that they will continue to make the final choice from the candidates whose names are sent to them by the new appointments commission.

The second point is that the commission itself will have to have real authority, enhanced by the inclusion of senior judges, if it is going to be a truly meritocratic, and not a quasi-political, body. Therefore, Lord Falconer, due to produce his proposals on the subject of the commission next month, may have to resist the depredations of his old friend David Blunkett, whose views on judges who stand up to ministers are rather well known.

One of Lord Irvine's signal services was to point out from time to time that, for all the talk about miscarriages of justice in the defendant's favour - the issue that is at the heart of the criminal justice reforms debated in the Lords yesterday - it was statistically a negligible cause of offenders not being brought to justice, and, by implication, failures of policing were a much more significant cause.

But beyond that, when, as he did yesterday, Lord Woolf, the Lord Chief Justice, in polite but unmistakable terms protests against the erosion of sensible discretionary rights of judges or the imposition by ministers of minimum sentences for murder almost whatever the circumstances, he argues for justice and posterity against the immediate political fashions of the moment. And the bigger the government majority, the more we should rejoice that such a figure exists.

This goes to the heart of the Government's need to defend its reforms to allcomers beyond the merely malevolent. Mr Blair is good at setting, as he will today, the Government's programme in an ideological context. But he heads a government that has so far changed much less in the country than many of his most fervent supporters hoped six years ago. That makes it all the more necessary to justify those changes he does choose to make with arguments of substance as well as form.

d.macintyre@independent.co.uk