The Army faces a battle to save its infantry battalions as Service chiefs fight to protect important equipment programmes in the most extensive review of Britain’s security for a decade.

Despite overstretched troops in Afghanistan, the Army could lose some of its 36 infantry battalions as every aspect of the £34 billion defence budget comes under scrutiny. The Army fears it may be particularly vulnerable as the other two Services have expensive equipment programmes under way, with billions spent or committed, while the high cost of nearly 100,000 soldiers’ salaries and allowances may be easier to cut.

The Ministry of Defence will produce a Green Paper for discussion early next year but any decisions will not be taken until after the general election, which must be held by June. The Conservatives have already made it clear that they would carry out a review if elected, and have hinted at 10 per cent cuts across Whitehall.

The timing of the announcement by Bob Ainsworth, the Defence Secretary, which the Tories said was at least two years late, appeared to some to owe more to politics than the needs of the Armed Forces. A Downing Street spokesman said Mr Ainsworth was instrumental in making the case for a review after taking over last month.

But John Hutton, whom he replaced, told The Times that MoD officials had begun talking about a review in February and he could have announced it himself. Defence sources suggested a desire to wrongfoot the Tories played a part in its timing.

The prospect of radical cutbacks will now hang over the Armed Forces for the next 12 to 18 months, while Service chiefs fight to preserve their pet projects. The possibility of three infantry battalions being cut or merged has already been aired in Whitehall.

Patrick Mercer, Tory MP for Newark and a former commanding officer of the Worcestershire and Sherwood Foresters, said: “There is more room for rationalisation within the infantry but to scrap three battalions would be demented.” More effort was needed to bring the Army to full strength of about 103,000, he said.

All big-ticket items are to be re-examined, from the two new 65,000-tonne aircraft carriers, which are to come into service in 2016 and 2018, to a £20 billion replacement Trident submarine force (by 2024), the Army’s £16 billion Fres (Future Rapid Effect System) armoured vehicles and the RAF’s Eurofighter/Typhoon aircraft.

The MoD carried out a review of equipment only seven months ago, resulting in a two-year delay in the construction of the carriers and a further postponement of most of Fres.

While the ministry will look for economies, many of its equipment projects are set in stone, taking up to ten years to come to fruition. The review might recommend a radical reshaping of the Armed Forces and a slimmed-down global security role for Britain but key decisions on expensive equipment have already been made, limiting the scope of the exercise.

MoD officials admitted that no programmes would be frozen to await the decision of the review. A defence source said: “Departmental business at the MoD has to continue, although as the work gets under way officials and ministers will be guided by what is being considered. What we can’t see is inertia being built in to everything the MoD does.”

With both Labour and the Tories committed to a defence review, it’s likely that the issue will become a significant topic for the election.

The three Service chiefs have spoken up for their own priorities, hinting at tensions ahead.

Admiral Sir Jonathon Band, the First Sea Lord, has championed the two carriers, despite their spiralling cost. Air Chief Marshal Sir Glenn Torpy, Chief of the Air Staff, has highlighted the crucial role of the Eurofighter Typhoon, costing more than £20 billion. General Sir Richard Dannatt, Chief of the General Staff, has cast doubt on “Cold War” equipment and has fought for a new generation of armoured vehicles for the Army, to replace the ageing Saxons, Scimitars, Spartans and Scorpions.

General Sir Mike Jackson, former Chief of the General Staff, told The Times: “I think it is right that defence gets a proper debate in the general election and if this preliminary work to a defence review proper achieves that, I think it will be a good thing.”

He predicted, however, that the hardest decisions on the future shape and scope of the Armed Forces would have to wait until after a new government was elected.

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