Selly Oak was commended for its high standards of care
Insufficient preparations are in place for a "significant" rise in injured servicemen and women, a cross-party committee of MPs has said.
The Public Accounts Committee called on the Ministry of Defence to make better plans in case its facility at Selly Oak, in Birmingham, should become full.
Most seriously injured troops go to Selly Oak Hospital, then on to Headley Court, in Surrey, for rehabilitation.
Surgeon Vice-Admiral Philip Raffaelli insisted the MoD could handle a surge.
The surgeon general for the armed forces said: "We showed last summer that we can cope with surges in casualty numbers."
Plans have been further developed and formalised since, he added.
However, the committee said it was concerned there was only a voluntary agreement with the NHS to take soldiers to other hospitals in the West Midlands.
It wants to see a "more robust" and detailed plan.
It also said the "military culture" at Selly Oak would need to be replicated at any new sites used by soldiers.
Conservative MP Edward Leigh, the committee chairman, said the MoD and its medical staff provided care comparable with the best NHS hospitals.
"What concerns us is the extent to which the MoD would continue to be able to provide that high standard of care if the casualty rate were to increase significantly.
"Selly Oak Hospital offers injured troops a military culture and environment, expertise in dealing with serious battlefield injuries and wider support for families."
The committee added that a "long-term challenge" was the lifelong care that a growing number of soldiers required.
It called on the MoD to work with other government departments to create a system to make sure soldiers' clinical care and support for their families was maintained.
About 565 servicemen and women have been seriously injured in Afghanistan and Iraq since 2001.
Surgeon Vice-Admiral Philip Raffaelli said, if faced with a surge in casualty numbers, they would first use available beds in all "clinically appropriate" Birmingham hospitals.
He added that an agreement had been made with the Department of Health and the NHS to use an alternative major trauma centre as an extra receiving unit and key staff would be detached there to provide clinical and military welfare support to patients and their families.
Veterans Minister Kevan Jones said he would consider the committee's recommendations, adding that contingency plans were already in place.
Shadow defence secretary Liam Fox said: "Selly Oak and Headley Court do great work but there is a fear that the NHS will not understand what our servicemen need.
"Those who are injured defending us deserve everything the country can give them."