The Ministry of Defence is revising the way it issues a controversial anti-malarial drug to troops on overseas operations amid fears it is ruining lives.
MPs earlier this year said there was ''strong anecdotal evidence'' that stringent conditions laid down by the manufacturers for issuing Lariam had been ignored by the armed forces.
It has been associated in a minority of users with depression, hallucinations and panic attacks.
In response to a critical report by the Defence select committee, the MoD has said it is revising malaria prevention policy to direct that all anti-malarial drugs are only supplied after a face-to-face travel health risk assessment is carried out.
Conservative Johnny Mercer, a member of the committee, said the MoD had failed to take the issue "seriously for quite some time".
He told BBC Radio Four's Today programme: "The evidence is very clear. Prescribing a drug outside the parameters clearly laid down by the manufactures is not acceptable."
The former army officer said the drug had been handed out without checking it was suitable.
"It was handed out without doing those risk assessments. Consequently there are a number of people in this country who feel that their lives have been ruined by taking this drug when they shouldn't have been."
While Lariam is not the main anti-malarial drug used by the armed forces, at least 17,368 personnel were prescribed it at least once between the start of April 2007 and the end of March 2015, according to official MoD figures.
The committee said it had received strong anecdotal evidence that a body of current and former service personnel had been adversely affected by its use and that the arrangements for supporting them were ''inadequate''.
While the manufacturer, Roche, had issued ''clear guidance'' that individual risk assessments should be conducted before prescribing the drug, the committee said the MoD appeared to have interpreted this to include ''desk-based'' assessments using medical records rather than face-to-face interviews.
The Defence select committee said the policy review was a "step in the right direction" but said it was "very disappointed" that its calls for Lariam to be designated a ''drug of last resort'' had not been acted on.
It said: "The committee welcomes the undertaking that, for military personnel, all anti-malarial drugs will be prescribed after face-to-face health risk assessments, and that checks will be introduced to ensure that when Lariam is to be prescribed, the patient must be offered an alternative.
"We also welcome the announcement that the MoD has established a single point of contact for present and former personnel who have concerns about their use of Lariam, as the committee requested.
"However, the committee is very disappointed that the MoD has yet to designate Lariam as a 'drug of last resort' as the report recommended.
"This would send out a clear message that the MoD has acknowledged and accepted the high risks associated with the use of Lariam and we urge the MoD to do this without further delay."