The MoD says people should donate to service charities instead
Members of the public are being urged not to send unsolicited Christmas presents to troops in Afghanistan.
The Ministry of Defence said mail from relatives was getting lost among gifts addressed simply to "A soldier" or to individuals not known to the sender.
It also said many presents were perishable and often went to waste.
Anne Forbes, from Operation Welly, which sends gifts to troops, said she took advice from military welfare officers on whom to send parcels to.
Capt Charlie Malcolm, who is in charge of post at Camp Bastion in Helmand province, said: "For personnel deployed overseas, personal mail from loved ones is very important.
"But the system can be completely overwhelmed by the public's generous donations, which results in mail from family and friends being delayed.
"The main cause of this is the huge and unmanageable number of welfare parcels, sent by well-meaning members of the public, to recipients not personally known to the sender."
The MoD said the onward delivery of parcels to troops on the front line required additional flights and convoys which placed the personnel manning them at extra risk of attack.
We work with welfare officers and all our parcels have names on them
Anne Forbes, Operation Welly
Many of the items sent were also either already readily available or "not suitable for the Afghan environment", it added.
A spokesman said some items were addressed simply to "A soldier in X regiment", but the armed forces nevertheless felt a moral obligation to deliver them because of the effort made.
Other parcels were addressed to individuals whose names had featured in news reports, he said, which could lead to them receiving hundreds of parcels from strangers.
Lt Col George Waters, who oversees operational welfare at the MoD, added: "There is no denying that the knowledge that complete strangers are thinking of you provides a boost to morale.
"But what the troops on the ground want above all else is to receive their personal mail and the sheer number of welfare parcels in the system causes serious delays to those all-important personal items."
Squadron Leader Nicola Parr explains other ways in which the public can help support troops
The MoD is asking people who wish to support British troops to give donations to recommended service charities, some of which do send parcels but in consultation with the military.
Armed Forces Minister Bill Rammell said: "It is very important to make sure that people express their support in the right way to make the biggest difference in helping our troops on the ground."
Operation Welly was set up by Theresea Evans whose son, Llywelyn, was killed in Iraq in 2003.
Mrs Forbes, who is the organisation's treasurer, said it worked closely with the armed forces.
"We work with welfare officers and all our parcels have names on them. We try to send parcels to those who don't have families," she said.
"It is the people who are sending gifts to 'A soldier in Afghanistan' that are holding things up."
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