A pledge to hit 500,000 coronavirus tests a day in the UK by the end of next month could be missed as vital chemicals and analysing machines needed to hit the target are “a few weeks” behind schedule, the body representing their manufacturers has said. Boris Johnson has insisted the UK will hit the target by the end of October, up from about 260,000 capacity now, despite a number of problems including people told to travel hundreds of miles and delays in getting results back. But the drive to boost capacity among testing providers to deliver the pledge is in doubt because manufacturers cannot make enough chemical reagents and analysers. The British In Vitro Diagnostics Association (Bivda) told the Guardian there would be “a lag” between the government target and the industry’s ability to scale up production and supply. Helen Dent, its chief operating officer, said: “If there was a steady order based on forecast numbers of tests that people are expecting, there would be a steady supply. But the manufacturing times for both reagents and analysers for the increased number of tests that are planned have a bit of a lag. “The lag is about a few weeks. It’s a supply chain lag in that everything is based on forecasts. So when there’s a forecast for a certain number of tests, the supply chain adjusts to that. And when the forecast is changed, the supply chain adjusts to that. The lag develops when there’s a new forecast, but then it [supply] catches up. But they have been ordered and they will arrive,” she added. Asked what the effect of a lag could be, Dent said the current situation – where demand for tests is outstripping supply up to fourfold – was an example. Jonathan Ashworth, the shadow health secretary, said: “Testing has become a shambles and it now looks like Boris Johnson’s promise of 500,000 test a day by October won’t be met.” Meanwhile, the Guardian has learned that ministers plan to spend more than £500m doubling the number of tests processed by laboratories at 16 hospital trusts as part of the effort to hit the 500,000 target. The NHS and Public Health England are currently able to process about a third of England’s testing capacity. The money, which the Department of Health and Social Care (DHSC) is preparing to announce, will pay for the physical expansion of existing facilities, purchase of equipment and hiring of clinical scientists. The government has told suppliers it wants to buy 300 extra analysers, which, using the reagents, disclose if a swab sample is positive or negative. It is hoped each can do 200 to 300 tests a day, boosting NHS capacity by 60,000 to 90,000. But one hospital chief executive said existing shortages of reagents and analysing machines would make it hard to expand NHS testing capacity quickly. “You live hand to mouth in terms of whether you’ve got the reagents or not. They’re in short supply, as are analyser machines,” they said. “If you’re going to expand these 16 hospital labs you need more analysing machines … The lack of them is an NHS-wide problem, a national and international problem.” Munira Wilson, the Lib Dem health spokesperson, said: “Ministers must break their dangerous habit of overpromising and underdelivering. It is eroding public trust.” The DHSC said the target would be met. “We are on track to have capacity for 500,000 tests per day by the end of October. We have a planned supply of reagent, allowing us to increase capacity in NHS laboratories. “We are also automating parts of the process, installing new machines, hiring more permanent staff, opening new labs and investing in new technology to process results faster,” a spokesperson said.