"We recommend that in the immediate future the government should refocus its efforts to concentrate its limited resources on one priority, namely security," the committee said.
The efforts to take a "comprehensive approach" linking security with development and governance in south Afghanistan were "faltering" and a growing list of responsibilities, including anti-drug fights, human rights and reconstructing seems too much for British military, the report said.
However, British Defence Minister Bill Rammell was quoted by Britain's Sky news as saying that "We are focused on security and I think, with respect, the Foreign Affairs Committee is a bit behind the game."
"It has always been about security, and indeed our revised strategy from earlier this year very effectively makes that point," he said.
Rammell rejected the claim that Britain's counter-narcotics responsibilities were distracting from the main military mission in Afghanistan. "I think the foreign affairs committee wildly overstates the amount of resource we are putting into the drugs fight," he said.
British troops suffered their highest casualty rate of 22 fatalities in July since the force began its deployment in 2001.
A latest poll showed that most British people oppose sending extra troops to Afghanistan and want to withdraw British troops from the country immediately.