LONDON (AFP/Reuters) - Lawmakers voiced concern on Thursday that a lack of helicopters was having adverse consequences on Britains campaign in Afghanistan after Prime Minister Gordon Brown denied it was fuelling casualties. A report from the House of Commons defence committee said a larger fleet would allow troops to undertake operations by air rather than on foot, which would improve their effectiveness and offer them more protection. However, the prime minister repeated his insistence that British forces had the resources and equipment they needed. British troops suffered their blackest 24 hours yet in Afghanistan last week when eight soldiers died during an ongoing assault against Taliban fighters in southern Helmand province, bringing the toll this month to 15. The deaths pushed the war to the top of the political agenda and the main opposition Conservatives who opinion polls suggest could win an election due within a year have accused the government of under providing for the army. Many of those killed in Afghanistan have been hit by improvised explosive devices (IEDs) that are hidden in the ground and are increasingly favoured by insurgents. Critics say more helicopters are needed to transport troops safely. We believe that the size of the fleet is an issue, and are convinced that the lack of helicopters is having adverse consequences for operations today, the defence committee report said. Its chairman James Arbuthnot added: We are concerned that operational commanders find they have to use ground transport, when helicopter lift would be preferred, both for the outcome and for the protection of our forces. The report called for an increase in the number of helicopters and training crews, arguing that upping flying hours is no substitute for more aircraft. It emerged Thursday that the head of the British army, General Richard Dannatt, had travelled in a US Black Hawk helicopter during a recent visit to troops in the troubled southern Afghan province of Helmand. If I moved in an American helicopter its because I havent got a British helicopter, he said. Speaking before a parliamentary hearing on Thursday, Brown insisted: For what were doing in Afghanistan weve provided the resources and equipment that are necessary. In a sometimes-testy exchange with Arbuthnot, a Conservative, Brown said the number of helicopters has increased by 60 percent in the past two years. The Ministry of Defence separately pointed to plans to invest six billion pounds over the next decade to increase the number further. Meanwhile, Prime Minister Gordon Brown said on Thursday that Afghanistan needed to do far more to make its troops available on the ground if a US-British offensive to secure territory ahead of elections is to succeed. Answering questions before a parliamentary committee, Brown repeatedly made the point that he did not think Afghanistan was pulling its weight and said he had spoken to President Hamid Karzai to try to address the situation. Im very clear that the Afghan army has got to do more, Brown said, arguing that any strategy to clear and hold large swathes of territory in the south ahead of a presidential election in August would hinge on Afghan forces. Im very clear that where we are in Helmand, we need the complement of more Afghan troops and police. And Im also clear that we have a role to play, and it will be a continuing role after the election, for some of our troops to mentor and train the Afghan security forces. He said Britain having boosted the number for a pre-election offensive, would review its numbers after the poll, and possibly in October, if the vote goes to a second round. But more immediately, he said there was not enough support from Afghanistans side to back up the efforts being made by Britain and the US. If Afghan communities were to be kept safe, it meant Afghanistan stepping up to the plate. We have been asking the Afghan national army through President Karzai to make available more Afghan troops on the ground, he said. It would be by far the best way of moving forward if once ground is taken by our troops, then local Afghan troops and police are there on the ground ... There are troops available and I believe they should be in Helmand for this campaign. The prime minister was also dismissive of the size of the Afghan forces, saying they would have to be substantially expanded if they were ever going to be capable of keeping control in a country the size of Afghanistan. Our ability to defeat a terrorist threat depends not only on what we can contribute militarily, but on what we can achieve by civilian as well as military effort in training the Afghan army, he said.