An infant dies every two minutes in Afghanistan, Unicef estimates
UK soldiers in Afghanistan should not carry out humanitarian work as it puts aid staff at risk, a charity has said.
Save the Children said the UK's policy of funding troops to work alongside aid workers threatened their impartiality.
The link-up on projects such as rebuilding schools blurred military and humanitarian objectives, it warned.
The Department for International Development (Dfid) said military and civilian efforts needed to be combined as security was such a huge problem.
The charity, which is launching a humanitarian appeal for Afghanistan, said the current policy could turn hospitals or schools, rebuilt with military help, into targets.
Its director of development policy, Patrick Watt, said aid should be handed out without military involvement.
"If aid is to be effective it must be planned and carried out in close and trusted consultation with affected communities," he said.
"It is clear that soldiers involved in the conflict in Afghanistan should not be carrying out sensitive and complex humanitarian work with vulnerable communities.
"It is only through impartial aid organisations, such as Save the Children, that essential rebuilding can be done safely and successfully."
The charity said its appeal aimed to help Afghan children caught up in the conflict, who now had the lowest chance in the world of surviving to their fifth birthday.
An infant died every two minutes in the war-torn country, according to the latest figures from UN agency Unicef.
Afghanistan Rights Monitor said 1,050 children were killed last year in suicide attacks, air strikes, explosions and crossfire - the highest annual total since the conflict began in 2001.
Mr Watt said children faced a massive humanitarian crisis with tens of thousands of families living outside the immediate conflict zones struggling to keep their youngsters alive.
Although Helmand province was among the most heavily aided places on earth, families outside the war zones had no access to medical treatment, clean water, or nutritious food, he added.
The Dfid said military and civilian efforts had to work together to support the Afghan government as security was a major problem in areas like Helmand.
A spokesman said real progress had been made, with the Afghan authorities, international community, aid agencies and local communities all pulling together in challenging conditions.
"Our aim is to help build a strong and stable Afghan government which can give its people the security, jobs and services they need," the spokesman added.
"That's why more than half of the UK's aid is channelled through the government itself to help strengthen its ability to serve the interests of its own people."