Patrick Mercer: There's no fat on the budget in the foxholes of Helmand

First, I very much regret that this letter has been leaked. It has got to be possible for Secretaries of State to communicate bluntly and openly with the Prime Minister before the public

get their eyes upon the nature

of such dealings. Government isn't easy – especially when

we are in such financial difficulties – and leaked letters don't make it any easier.

However, the essence of the letter is simple. It points to the fact that mismanagement of the Armed Forces coupled with understandably expensive campaigns has already led to the defence budget being heavily overspent.

If further cuts are ordained by the Treasury, then they will add to the existing overspend and essentially double the savings that are being asked of the Ministry of Defence (MoD).

To paraphrase the letter further, that would be fine if the MoD's case were not unique. Other departments have to provide health, policing etc, but nobody else fights wars.

Now, I see no reason why the MoD should not be asked to make some cuts. However, those must be balanced against the fact that if we continue to under-resource our Forces in Afghanistan then lives will be frittered away.

Dr Fox makes the very legitimate point that we can't fight wars on the cheap – the Labour Party tried that. The endgame in Afghanistan has got to be the rebuilding of that country and its forces so that it can stand full square on the flank of Pakistan and so that some equilibrium can be returned to the region as a whole.

That will be neither easy nor cheap but the consequence

of getting it wrong is more scenes such as those that occur too frequently at Wootton Bassett.

It is a sobering thought, but Britain can now only deploy about nine thousand "fighting troops" at any one time. That sounds crazy when the size of the Army, Royal Marines etc. stands at well over 100,000. But when you do the sums, that is all that comes out at the end.

To support those 9,000 troops should be perfectly possible even with the reduced defence budget but it is crucial that those men have the equipment, the aircraft and the reinforcements that they need.

There are complex arguments about where the cuts should fall. Some say that the Royal Air Force's Fighter Force should be drastically reduced, some say that we don't need the two new aircraft carriers that are bound for the Royal Navy and others suggest a cut in Army manpower. Well, Dr Fox's letter, which I support entirely, indicates that we should start with the top-heavy, bloated bureaucracy of the MoD first rather than with the frontline.

Here are some suggestions. If we have more civil servants than we do soldiers, let's get rid of some civilians. Next, there are five major headquarters all stuffed with generals, air-marshals, admirals and top ranking civil servants. Why do we need such talking shops when we have got only 9,000 bayonets in the field: cut them. And if you want to drill down further why are there 30-odd brigadiers with no proper jobs to go to?

There is plenty of fat here which there isn't in the foxholes on the Helmand.

It's also worth noting that the threat from Irish dissidence has risen and that an ambitious plot to attack the UK mainland by al-Qaida has also come to light. Our security isn't just about Afghanistan and Pakistan, it is about our streets and cities which will only be kept safe by sophisticated and resilient defences. Those must not be cut.

Lastly, what about the timing of this leak? Whoever did it is clearly aware that it will propel defence discussions into the forefront of the Tory Party Conference. For my money, that is a good thing – but I regret the means by which it has been achieved.