The Taliban have killed 1,100 members of the Afghan security forces in the past six months as Nato troops have stepped back and left the local army and police to fight the insurgency, it has emerged.
Philip Hammond, the defence secretary, admitted there had been a doubling of casualties among Afghan National Security Forces (ANSF) over the past year, as well as spikes in desertion rates from the army.
The previously classified figures were given to the Ministry of Defence by commanders at Nato's International Security and Assistance Force (Isaf) to help Hammond and Lieutenant General Richard Barrons prepare for questions from MPs.
Asked about Afghan casualties, Hammond said the evidence pointed to a sharp increase.
"We have to enter caveats about the quality of data and baseline data, but as the Afghans have taken over the leading role in security, clearly their casualties have gone up very significantly. Possibly they have doubled over the last year or so."
Barrons said the ANSF had suffered badly from attacks by improvised explosive devices (IEDs) in the past six months. Without the same medical and logistical support of western forces, the Afghans had been hit hard, he said.
"In the last six months, there has been an increase in IED attacks on the ANSF, and they are taking substantial casualties, roughly 1,100 fatalities. It is a significant issue, but the [Afghans'] ability to deal with it is getting better."
Later, the MoD confirmed the 1,100 referred to deaths across Afghanistan among forces that now have the prime responsibilty to take on the Taliban.
The general admitted the attrition rate for the 350,000-strong ANSF – the number of personnel deserting and not returning to their posts – was also higher than it should be.
The target was to keep the levels to 1.6% of the force deserting every month. But the monthly average was 2.6% – and last October it peaked at 3.1%.
The general said the key to stopping desertions was "good leadership, decent pay, decent food and the end of corruption".
Hammond told the defence select committee an Afghan food supplier had recently been jailed for supplying substandard rice to the Afghan National Army.
He denied the insurgency was making ground, and said two recent Taliban attacks in the capital Kabul had highlighted how desperate the insurgents had become.
One was against the intelligence agency, the National Directorate of Security (NDS), and the second was against the Afghan traffic police.
"All the evidence I see is that the Taliban is struggling to maintain the momentum of the insurgency and there is absolutely no evidence to suggest they have the reserves to press a button and significantly increase the tempo of the insurgency," said Hammond.
"The two incidents that occurred in Kabul were both attempts at spectacular attacks in an area that is pretty safe. The first on the NDS was a failure. The second was on a very soft target, unarmed Afghan traffic police.
"This doesn't look to me like an insurgency with a lot of reserve firepower."
Hammond predicted that when international troops end their combat role next year, Afghan forces would be able to "effectively hold the important parts of the country", such as cities, towns and key infrastructure.
"I would expect the situation to be messier than it is today, but I sense that there is a growing recognition on both sides of this fight that neither side can win outright. The government cannot defeat the Taliban and secure every inch of Afghan space.
"The Taliban sense, and we have some evidence of acknowledgement of this, that they cannot defeat the government in military terms. So I think both sides will want to make progress ultimately to some kind of political accommodation."
Hammond added: "Our own experience suggests that might not be a smooth process. It might go in fits and starts. But I would expect slow and messy progress."