text: Off target: It has been claimed the G36 (pictured) does not shoot straight when it overheats at 30C . The G36 was created for the requirements of the German armed forces but it is also used as an infantry weapon in around 50 countries. It is used in Britain by counterterrorism police. First made: 1995 . Calibre: 5.56 mm x 45 . Magazine capacity: 30 rounds . Weight: 3.63kg . Length:  755-1,002mm . Use in the UK: Between 2,000 and 3,000 G36 rifles belong to police forces across the country . An assault rifle used by counter-terror police does not shoot straight when it gets hot, tests claim. The Heckler & Koch G36 is inaccurate by up to 20 feet at long range when temperatures top 30C, it was found. The weapon also becomes unreliable when it is left in direct sunlight, exposed to humidity or fired repeatedly, according to a confidential report. The findings have prompted an urgent inquiry into the German-made firearm, which is used by law enforcement officers across the UK. Britain's police forces use a short-barrelled version of the weapon known as the G36C – and have a total arsenal of up to 3,000. Counter-terror and armed response unit officers use them when they need more firepower than the 9mm pistols or carbines they usually carry. Now experts at the Home Office's Centre for Applied Science and Technology (CAST) will lead the inquiry after Germany said the rifle had 'no future' with its military. A leaked report commissioned by Berlin's defence ministry said the precision and accuracy of the G36 deteriorated when it overheated, either because of the temperature or rapid fire. It concluded that when the atmospheric temperature reached 30C (86F), bullets missed their mark by about 50cm (20 inches) at a range of 200m (220 yards) and by up to six metres – about 20ft – over 500m (546 yards). Reports in the German media claimed it also started to become seriously inaccurate after it fired just two magazines – about 60 rounds. Heckler & Koch denies the weapon is inaccurate. But Britain's National Police Chiefs' Council has asked CAST to consider the findings. Simon Chesterman, spokesman on armed policing, said: 'The reliability of any weaponry that the police service uses is of paramount importance.' Superintendent Kevin Carter, of the Civil Nuclear Constabulary, which guards Britain's atomic plants, said it had not experienced problems but added: 'We will monitor the situation and await advice from CAST.' UK police are said to be desperate for a new firearm to help curb the threat of terrorists carrying high-velocity automatic weapons and using body armour. Officers are finding it increasingly difficult to maintain their ageing armoury and are concerned by the discovery of heavy weapons among criminal gangs. Under review: Deputy Chief Constable Simon Chesterman (pictured), the spokesman on armed policing at the National Police Chiefs' Council, has said the findings will be referred to the Home Office for urgent review . In service: The weapon is used by police forces across the UK. They have a total arsenal of between 2,000 and 3,000 G36C rifles, a version that has a shorter barrel than Heckler & Koch's standard-issue rifle . The G36, created in the early 1990s for German troops, is also used in around 50 other countries. British Special Forces used it in Iraq but reports surfaced in 2012 that G36s used by German soldiers in Afghanistan would overheat during prolonged firefights. In the German report, experts tested 304 rifles – including the short-barrelled version – and found none passed precision tests. They concluded: 'The causes for the reduced accuracy do not lie in one of the components... but rather in the whole system.' Lieutenant-Colonel Markus Thull, of the German defence ministry, said the G36 was now 'not fit for purpose'. Andreas Heeschen, of Heckler & Koch, said the rifle complied with its original specifications, but a gun 'designed for the Cold War' did not meet current requirements. He added that the company had received no complaints from the 50 countries where the weapon is used but vowed to assist with the UK review.
target: Leaked report suggests G36 rifle did not shoot straight when it overheated .
  German army carried out tests and none of the 304 assault rifles passed .
  The weapon is used by British counterterrorism officers across the UK .
  An urgent Home Office review has been called for in light of the findings .