Public services in Scotland’s poorest areas could be harmed by widespread abstention from this year’s census in urban areas, experts fear. Public policy specialists and opposition parties are alarmed after it emerged that by Monday only 86% of households nationwide had filled it in, well short of the 94% target, despite a four-week extension to the deadline until 31 May. The Scottish government delayed the census until April despite it being held across the rest of the UK last year. Staged online by default for the first time at a cost of £150m, it is expected to miss all its key targets. One target described by National Records of Scotland as a “critical success factor” was to achieve a minimum response rate of 85% across all 32 of Scotland’s local authorities. By Thursday last week, 25 council areas had passed that threshold. In areas with Scotland’s highest rates of deprivation it was about 80%. In Glasgow it was 79%, West Dunbartonshire 80%, Inverclyde and Dundee 82%, and in North Lanarkshire 83%. Philip Whyte, the director of the public policy thinktank IPPR Scotland, said the low response rates were significant given that the census provided “vitally important” data that helped underpin policies and spending in health, education and social services. “It’s hugely concerning that areas with some of the highest levels of deprivation in Scotland, like Glasgow and West Dunbartonshire, haven’t even seen an 80% census response rate yet,” he said. “Scotland has some very welcome ambitions to secure a more inclusive economy but poor-quality data will make that task harder. Policymakers must ensure public services in areas with high levels of deprivation do not see any negative impacts as a result of potentially skewed census results.” The census deadline was extended in late April after Angus Robertson, the Scottish constitution secretary, said 23% of Scots had not yet responded. He warned householders they risked a fine or even a jail term for failing to complete it. National Records of Scotland said its census field teams and publicity campaigns would be shut down on Wednesday. Paul Lowe, its chief executive, urged people to fill in their forms before the deadline. “Big decisions about our local communities and our nation as a whole are based on census data. Everyone’s circumstances need to be captured to ensure the best decisions are taken, so please complete now,” he said. Sarah Boyack, Scottish Labour’s constitution spokesperson, said: “It has been one [Scottish National party] shambles after another recently, but this mess will take years to clean up. “Without action this will deliver a decade of injustice in Scotland as the worst-off communities are left paying the price for SNP failure. The SNP must set out how they will make sure this botched census doesn’t leave the poorest areas shortchanged.” Nicola Sturgeon, the first minister, indicated 10 days ago there were questions about the census’s credibility. “Work will be done to ensure that the exercise has been a credible one and that the information that was gathered is reliable. It will be appropriate to take expert advice on that,” she told MSPs.