Conservative MP Patrick Mercer, a former Army officer, said security and overseas aid were "inextricably linked".
He told BBC Radio 4's Today programme: "I absolutely understand the need for overseas aid although not necessarily at this level.
"But I do see that so much of the aid we have attempted to spend in the past in places like Iraq and Afghanistan has not been delivered as effectively as it might because of the lack of a benign security environment.
"If that means more money has to be spent on defence in order to increase the efficacy of overseas aid spending, I'm all for it."
More top news
Andy Murray is Britain's last hope of a 2015 Wimbledon win after overcoming an apparent shoulder injury to beat Italy's Andreas Seppi.
New Tour de France time-trial record set after Australian Rohan Dennis raced into the lead during Stage one of the competition.
Fresher and cooler as we head into the second half of the weekend.