The Roman Catholic Bishop of Menevia, Tom Burns, voiced his criticism at the funeral of Royal Welsh soldier Jonathan Burgess, from Swansea.
The fusilier, from the Townhill area of the city, died from gunshot wounds while on patrol in Helmand province.
The 20-year-old was expecting a baby girl with his fiancée.
The bishop said Fusilier Burgess, from 1st Battalion The Royal Welsh, would be "etched in the history of the battalion forever" as he said the price of war had been high.
He said: "To our politicians and civil servants I ask these questions: When will Afghan institutions rise out of the dust to take responsibility for their own affairs?
"When will there be a surge in funding to achieve this and for ongoing military vehicles, more and better helicopters and better intelligence - all of which are so badly needed?
"If this were done surely this will mean fewer lives will be sacrificed in the future.
"For Jonathan is the kind of young man we need in Britain today. We cannot afford to lose him and others like him. Why should there be any more excuses? What else is there to be done than this?"
Bishop Burns has extensive military experience and has worked on the frontline of Iraq, as well as being a Royal Navy chaplain.
He was appointed Bishop of the British Forces in 2002 and has involvement with the military stretching back 25 years.
Extensive tributes were paid to Fusilier Burgess following his death on 7 April.
Senior officers said he was a natural leader who had been marked out for early promotion.
He joined The Royal Welsh almost two years ago and during his four months in Afghanistan had been a key member of 3 Platoon, conducting aviation assault and ground holding operations.
He was engaged to be married to Kelly Forrest and also leaves behind father, Royston, mother, Susan, sisters, Tracy and Suzanne, and brothers, David, Christopher and Ashley.
In a joint statement issued via the Ministry of Defence at the time of his death they said: "Jonathan was a loving and caring man who enjoyed life to full.
"He had an infectious smile that would brighten up anyone's day. We were all very lucky to have had such a wonderful person in our lives.
"He was a much loved son, brother, friend and fiancé and would have been an amazing father to his baby girl.
"He will be greatly missed by us all. He will always be our hero."SIC: BBC