Lib Dem MP Simon Hughes said in a debate in Westminster Hall that the government should not reduce spending on conflict prevention and peace keeping.
"For every dollar that is spent on conflict prevention, states spend some $2,000 on weapons and military budgets - that is an absolutely central and telling fact," he said.
"Can we afford not to increase the level of money spent on reducing conflicts, given that the long term costs of conflict are so high?"
Mr Hughes, a co-chair of the All Party Parliamentary Group on Conflict Issues, said concentrating on conflict prevention would give the world a better chance at a more peaceful future.
Foreign Office Minister Ivan Lewis said the FCO had to prioritise certain areas over others given the "difficult and challenging" financial environment.
"We will continue to deploy the right people to the right place, at the right time, to help rebuild countries recovering from conflict," he said.