British troops wounded in Afghanistan are enduring lengthy delays before receiving hospital treatment because of a shortage of helicopters, senior army surgeons have claimed.

Medics in Helmand province, where another soldier died yesterday, said a lack of British aircraft meant that bringing out wounded soldiers takes twice as long as when injured American soldiers were evacuated in Vietnam 40 years ago.

An experienced combat surgeon revealed that the lack of helicopters meant UK forces would find it "impossible" to transport their wounded if they did not have access to US Black Hawks. One said that up to 50% of all British "casevacs" - casualty evacuations - use American helicopters.

The surgeon, who asked for anonymity, also revealed that the Royal Army Medical Corps and senior military figures had been asking for a dedicated fleet of medevac helicopters since 2007, but their pleas have been rejected by Whitehall.

Only two British helicopters, at most, are reserved for attending to wounded soldiers, according to medics, which is not enough to cover the battlefield of Helmand.

According to the Ministry of Defence, the average time from injury to handover at a field hospital is one hour 45 minutes, or an hour and 29 minutes for the most severe casualties. In Vietnam, American troops arrived at hospital within 45 minutes, most of them within 25. Reports from surgeons currently based in Helmand to military colleagues have revealed the intensity of opposition facing UK forces. They show that the major field hospital in Helmand, at Camp Bastion, has been using almost four times more blood for transfusions - 42 units a day - than an average general hospital.

Major Mike Taylor, medical liaison officer at Task Force Helmand, said helicopters are available 24/7 to evacuate wounded personnel. He said that during current operations, there had never been an occasion where a clinical timeline to get a patient the treatment they required had been missed.

Amid increasing casualties, the MoD is to go to the court of appeal on Tuesday in a bid to overturn rulings that two injured troops should have their compensation increased following complications after initial medical treatment.

Other wounded soldiers could be in line for higher payouts if the appeal is unsuccessful.

• The MoD confirmed the death of another soldier in Helmand yesterday, the 20th to have died in southern Afghanistan this month. The latest fatality, from the 40th Regiment Royal Artillery, died while on a vehicle patrol north of Lashkar Gah.