It was Jack Straw, the only new Labour home secretary to survive a full term, who summed up the difficulties of the job. “At any one point there are 20 civil servants taking decisions that could lead to your resignation. The question is knowing which 20 they are.”

Straw wasn’t joking: the problem of knowing who holds the hot potato finished off Charles Clarke, who was forced out of office as a result of the foreign prisoners fiasco last May. Overzealous action by an official who fast-tracked his lover’s nanny’s visa application did for David Blunkett.

The Home Office’s recent troubles have lurched from high seriousness to farce — from the absconding of more than 20 murderers from open prison to the discovery of five Nigerian illegal immigrants working as cleaners at the immigration division.

Last week John Reid, the political bruiser brought in by Tony Blair to sort out the mess, announced his “rescue plan” for the beleaguered department. The plan involves the immediate removal of 15 Home Office directors and the streamlining of headquarters staff so more can work on the front line.

Reid also flagged up tough new sentencing plans that should make it easier for judges to send paedophiles and other serious offenders to prison for longer terms. The sentencing proposals should allay public concern, but the “rescue plan” is unlikely to convince seasoned observers of the department, a large part of which Reid himself only recently admitted was “not fit for purpose”.

There are a number of theories as to what is wrong with the Home Office. The first lays the blame on the scope and structure of the department itself: from terrorism to immigration and asylum; policing to prisons; and antisocial behaviour to sentencing, its remit is simply too vast and too complicated for any single cabinet minister to grasp.

A second is that the “dynamic” of the department is different from every other ministry. Its “customers” are criminals, terrorists, failed asylum seekers and illegal immigrants — any one of whom can create a headline at any time, if administrative or official incompetence allows.

Or it may be, as Tories and Liberal Democrats, suggest, that the mess is caused by Labour’s obsession with headline-grabbing announcements that look effective but rarely work.

As the name implies, the Home Office once had responsibility for all domestic affairs. Subsequent domestic departments were in effect created by taking away some of its responsibilities.

What remains is national security and law and order, plus an assortment of other issues: race equality, charities, the voluntary sector, the regulation of animal experiments, the Mental Health Act, forensic science, nationality and immigration and “design and green issues”. Home secretaries find themselves dealing with matters as diverse as wild birds in Scotland and which towns in England and Wales are entitled to call themselves cities.

But if the Home Office is inherently complex, experts say Labour has made it more so. Last week’s barrage of announcements, carefully trailed and extended over a period of days, was typical, and the tendency to grab headlines comes from the top: Tony Blair's own ill-judged forays into criminal justice have included “eye-catching initiatives” such as marching yobs to cash machines, or clearing the judicial backlog with night-time sessions at court — both quietly abandoned within days.

In 2001, the government launched a “10-year strategy” for dealing with criminal justice. Three years later Blunkett announced the Home Office’s “five-year” strategic plan. Then last year Clarke produced his own plan to reduce re-offending.

Richard Garside, acting director of the Centre for Crime and Justice Studies, asks: “Is the 10-year plan still in position or not? Is the five-year plan still in place?” Garside calculates that between 1997 and 2004 Labour brought in almost 50 criminal justice acts. “They seem to have legislative overkill,” he says. For professionals expected to implement the new initiatives, it’s become impossible to keep up.