When Gordon Brown was presented with four options on how best to boost the British campaign in Helmand, he chose the cheapest, authoritative sources disclosed yesterday.

While the service chiefs and John Hutton, then Defence Secretary, supported the option of sending an extra 2,000 troops to Afghanistan, the Prime Minister opted only to send a 700-strong battalion for a limited period.

With the approval of Alistair Darling, the Chancellor, he announced in April that the 700-strong deployment would boost numbers during the period of the presidential election, set for August 20. Mr Brown’s rejection of the more expensive options was a setback for the military establishment.

The heads of the three Armed Services, the Chief of the Defence Staff and Mr Hutton had all agreed that the British Task Force in Helmand needed 2,000 extra permanent troops to improve conditions in the province. They believed that the success of the mission was at stake and failure to send more troops would undermine the progress that had been made with great loss of life by the British Forces, and let the Taleban off the hook.

“But the Treasury put a total block on spending more money, and the Foreign and Commonwealth Office was against it, too, so the Prime Minister went for the least expensive option,” one source told The Times.

The leading figure behind Option D, the 2,000 extra troops, was General Sir Richard Dannatt, the Chief of the General Staff. He persuaded his fellow chiefs — Admiral Sir Jonathon Band, First Sea Lord, and Air Chief Marshal Sir Glenn Torpy, Chief of the Air Staff — that the British troops needed reinforcing to consolidate military progress and add force protection to the units already in Helmand. Air Chief Marshal Sir Jock Stirrup, the Chief of the Defence Staff, concurred.

The setback was felt not only by General Dannatt, who had revealed his wish for 2,000 more troops in an exclusive interview with The Times in March. It was also a blow to the morale of the military establishment as a whole, which for years had felt that the Treasury, in the hands of Mr Brown when he was Chancellor, had placed the Armed Forces low in the list of spending priorities.

Long gone were the days when a service chief in his uniform would stride across Whitehall and knock on the door of No 10 to plead his cause to the Prime Minister.

The service chiefs felt that there was no point because Mr Brown, both at No 11 and at No 10, was not going to be an interested listener.

The Armed Forces’ cause had also not been helped by a growing antipathy between the individual service chiefs who, under financial restraints, were having to fight their corners to save key equipment projects that led to inter-service rows. Air Chief Marshal Stirrup was caught in the middle and relations have been difficult.

The timing of the request for the equivalent of another battle group for deployment in Helmand was crucial. The military commanders in the province wanted the extra troops before the Taleban fighting season got under way.

The argument was that the extra 2,000 troops could be used to train the Afghan National Army and Afghan National Police — “this was our exit strategy after all, just as it was in Iraq” — and also to “thicken” the existing battle groups, which were short of numbers, the source said.

General Dannatt considered that a total force of 10,000 was the minimum required. He would have wished for a task force of 12,000 troops, but he knew that that would have placed intolerable strains on the Army — the same overstretch pressures that the Service had faced when it was fighting two wars simultaneously, in Iraq and Afghanistan.

Air Chief Marshal Stirrup had said publicly that there was no intention of transferring the 4,100 troops in Iraq to Afghanistan in a “like-for-like” deployment.

“There were very sound reasons why the Ministry of Defence as a whole felt that it was important to send 2,000 extra troops at a time when it was likely to have a maximum positive impact on the campaign. The trouble was that we just didn’t have enough troops to hold the ground we had taken,” one source said.

The 700 extra troops provided were a mixed bag, a combination of infantry — two companies from 4 Rifles — and Royal Engineer squadrons to carry out counter-IED operations.

Mr Hutton resigned in June before the Prime Minister’s reshuffle. He had told Mr Brown three weeks earlier that he wished to step down as Defence Secretary. His decision was not connected with the troop rebuff delivered by No 10 in March.

— Details from the journal of a Welsh Guards platoon commander who died in May after being injured in Afghanistan were published last night.

Lieutenant Mark Evison, 26, wrote: “I have a lack of radios, water, food and medical equipment. This, with manpower, is what these missions lack. It is disgraceful to send a platoon into a very dangerous area with two weeks’ water and food and one team medics’ pack. Injuries will be sustained which I will not be able to treat and deaths will occur which could have been stopped. We are walking on a tightrope and from what it seems here are likely to fall unless drastic measures are undertaken.”

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