The unit investigating claims of abuse by British forces in Iraq is to close down, the government has announced, saying it will also greatly reduce similar inquiries connected to Afghanistan and Northern Ireland. Ministers said the decision was made after misconduct findings against a solicitor involved in many of the claims. However, rights groups said it was important abuse was not “brushed under the carpet”. The Iraq historic allegations team (Ihat) will close as early as this summer, the defence secretary, Michael Fallon, said on Friday. Any remaining investigations – expected to soon fall to about 20 from a peak of 3,000 – will be investigated by the Royal Navy police. They would be expected to complete any final investigations by the summer of 2018, Fallon added. He said the decision was made after the campaigning human rights lawyer Phil Shiner was struck off this month over multiple professional misconduct charges, including dishonesty and lack of integrity. Shiner had led legal claims against British troops for their treatment of Iraqi detainees after the 2003 invasion. His company, Public Interest Lawyers (Pil), was involved in passing on almost two-thirds of the 3,392 allegations received by Ihat. Shiner had pursued the case of Baha Mousa, a Basra hotel worker whose death after 36 hours in British military custody prompted an inquiry which condemned the treatment of detainees. However, other allegations turned out to be untrue. In 2014 the long-running al-Sweady inquiry rejected claims that British soldiers murdered insurgents and mutilated their bodies. Shiner later admitted paying an Iraqi middleman to find claimants, in breach of professional standards. His downfall was “the beginning of the end for Ihat”, said Fallon. “This will be a relief for our soldiers who have had allegations hanging over them for too long. Now we are taking action to stop such abuse of our legal system from happening again.” As part of this process, the Royal Military police is to discontinue about 90% of 675 allegations of abuse from Afghanistan, a Ministry of Defence statement said. For historical investigations in Northern Ireland, the government will ensure “veterans and former police officers are not dragged through the courts in disproportionate numbers compared with terrorists”, the statement added. General Sir Nicholas Carter, chief of the general staff, said credible abuse claims should be investigated. “However, a significant number of claims made against our soldiers have not been credible,” he added. A winding down of abuse inquiries has been called for by some Conservative MPs and newspapers. But Amnesty International said the failings of Shiner and his firm should not mean all abuse claims were dropped. “As we know from Baha Mousa’s torture and killing as well as the fatal forcing into a canal of a 15-year-old boy in Basra, UK forces in Iraq did some terrible things to people in their custody,” said Allan Hogarth, Amnesty’s UK’s head of policy. “These weren’t isolated cases – numerous other cases involving alleged abuses of Iraqi detainees by UK military personnel have been settled out of court by the MoD. “We’ve always said it’s vitally important the UK sets an example internationally by making sure any credible allegations of human rights violations are both independently and thoroughly investigated. “The UK’s military reputation is on the line – any credible allegations of abuses by UK forces in Iraq and Afghanistan should be independently investigated, which must mean by a body that is separate from the military itself.” The government has previously committed to ending what it calls an “industry of vexatious claims” against soldiers by allowing the military to opt out of the European convention on human rights (ECHR) during future conflicts. While derogating from the ECHR in times of war or public emergency is permitted under the rules of the Council of Europe, which oversees the treaty, the plan has also been condemned by rights groups.