THE SCOTTISH Government has extended the deadline for the census by another two weeks.

It is the second time ministers have been forced to push back the final date for returns.

The £150 million research project, which was decoupled from last year’s census in England and Wales, is expected to miss all of its key targets.

By Monday only 86.6 per cent of households nationwide had filled it in, far short of the goal of 94%.

In England and Wales, 97% of households filled in the form. 

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.

But by Thursday last week, only 25 council areas had passed that threshold. 

The return rate was lower in regions with high levels of deprivation. In Glasgow it was 79%, West Dunbartonshire 80%, Inverclyde and Dundee 82%, and in North Lanarkshire 83%.

The National Records of Scotland (NRS) has yet to provide the figures for the last 48 hours.

During Wednesday's First Minister’s Questions. Nicola Sturgeon insisted the exercise was still credible. 

“NRS are confident that the national return rate and the coverage across the country coupled with the normal planned post collection, quality control and assurance will provide credible, high-quality outputs,” she told MSPs.

The First Minister said that lessons would be learned. But, she added, there would, as normal, be a census coverage survey, which would involve door to door interviews with a sample of around 1.5% of the Scottish population, about 50,000 households. 

"That survey alongside the use of other data builds on the census returns so that the census outputs are representative of the whole of Scotland's population, and therefore that does address the concern about those in our more deprived communities," Ms Sturgeon told MSPs.

Labour's constitution spokesperson Sarah Boyack said The First Minister’s response was "about as credible as this census data."

She added: “It is farcical to see Nicola Sturgeon insist everything is going to plan while her government scramble to push the deadline back for a second time this year.

“While the public are still being kept in the dark about the latest return rate, the chances of the government meeting their targets are approaching zero.

“We need a genuinely credible plan to fix the mess the SNP have made of this or it will be the poorest communities who will pay the price.“

Donald Cameron, the Scottish Conservative constitution spokesman, said: “This whole process has descended into chaos — and it’s a shambles entirely of the SNP government’s making.

“We warned them of the perils of not running the census in sync with the rest of the UK last year. But, as usual, they had to be different and do their own thing — squandering the benefits of the UK-wide publicity drive in the process.

“The census completion rate is so low that — despite one embarrassing deadline extension already — the data obtained still risks being insufficient and not fit for purpose.”

Those who don’t return their census can be fined up to £1,000. 

However, In England and Wales, the Crown Prosecution Service took 286 non-completion cases to court, with 270 resulting in convictions. Of these, four received the maximum fine of £1,000, the amount imposed in other cases varied with the average fine amounting to £217.99.

In December 2011, just five cases of non-completion were prosecuted in Scotland.