Britain’s defence secretary hit back on Thursday at accusations that cuts to army numbers put the country at risk and reduced its standing as military power, as he outlined a major shake-up of the force’s structure.

Philip Hammond said Britain’s army, whose regular trained members will be cut to 82,000 from 102,000 by 2020 to save money, would still be able to deploy a similar-sized force to that sent to Afghanistan.

“Despite what you read in some of your papers, people could be forgiven for thinking that we are nowhere in the military pecking order. We do have the fourth-largest defence budget in the world and the army is one of the top-performing armies in the world and will remain so,” he told reporters.

Hammond plans to shift the army away from what he said were the “predictable” duties of Afghanistan, from which Britain plans to withdraw the bulk of its 9,500 troops by 2015, to a more flexible force more able to deal with contingencies.

Under the plan, the army will be split into three broad divisions: a high-readiness “reaction force”, an “adaptable force” held at a lower readiness and a “force troops” division to provide specialist support.

“Part of the design specification for this (restructuring) is the continued ability to deploy a brigade-sized force on a continuing operation indefinitely as we have done in Afghanistan,” Hammond said.

Hammond aims to make up for cuts to the regular army by doubling the number of reservists to 30,000 and boosting their training and responsibilities. By 2020, he expects the combined army of regular soldiers and reservists to reach 120,000.

However, doubts remain whether employers will spare workers for long deployments and whether reservists can really substitute for professional soldiers.

“It is inconceivable that there won’t be an impact on force projection .... Today’s plans may provide flexible forces, but it’s far from certain that they will provide sustainable military utility,” opposition Labour Party defence spokesman Jim Murphy told parliament.