A further 900 British military personnel will be deployed to Afghanistan to help the reconstruction effort, the defence secretary has announced.
Des Browne's announcement follows an "urgent" request from commanders on the ground, and will take the total number of UK troops in the country to 4,500.
The level of violence in the southern province of Helmand has escalated in recent weeks, where British troops are among the Nato forces struggling to restore security.
Six British soldiers have died in the past four weeks in clashes with the Taliban, prompting widespread concern that the deployment sent earlier this year was inadequate.
However, speaking to MPs this afternoon, Mr Browne rejected this analysis, insisting the government had made clear from the start that although British forces in Afghanistan were not there to fight terrorists, violent resistance was expected.
"We always knew that there was a problem of violent resistance - that is why we sent soldiers to do this work. But this doesn't change their role of reconstruction," he said.
He admitted that violence had increased since the British forces arrived, but said this was "inevitable", adding: "We are challenging the power of the Taliban and they are reacting, but despite that we are spreading security."
The defence secretary said this success was partly the cause of the new deployment - although the original plan was to move out from the centre of Helmand, commanders on the ground had an "early opportunity" to move north and took it.
"We are moving faster towards our ultimate objectives but we extended ourselves. This is a development we must respond to, but it was our actions that brought about this - not a failure to anticipate the violence response to our arrival," Mr Browne said.
Liberal Democrat defence spokesman Nick Harvey welcomed the new deployment, saying the loss of six soldiers had "forced a sober realisation of the challenges ahead".
"In January the mission was described by the former defence secretary as a small but significant step, yet the increasing violence proves otherwise," he said.
"In the aftermath of the Iraq war the UK and US turned their backs on Afghanistan with obvious consequences. What is needed is a clear operational strategy with achievable objectives."
Today's deployment will include 320 engineers and 400 reservists, and helicopters. It takes the percentage of the UK armed forces on operation to 18 per cent, which Mr Browne said was "challenging but manageable".