Parents across Scotland were unable to apply for a new expanded benefit of £25 a week after the Scottish Child Payment website crashed on its launch.
The application page for the payment, for which around 400,000 children are now thought to be eligible, failed to load for several hours on Monday morning due to “exceptional demand”.
Social Security Scotland apologised to families and said it was working to fix the issue as quickly as possible.
The website was live again by midday.
It comes after the Scottish Government urged parents to apply for the benefit which is unique to Scotland.
Social Security Scotland previously said it expected a large number of new applications, meaning those applying for the first time may need to wait to get their award.
Previously, the Scottish Child Payment was paid to low-income families with younger children, however it has now been extended to all eligible households with youngsters under the age of 16.
The payment, which has been hailed by First Minister Nicola Sturgeon as the “most ambitious child poverty reduction measure in the UK”, has also been increased from £20 a week per child to £25.
It means eligible families will receive £1,300 a year per child.
Parents can apply online through the Social Security Scotland website.
Those who do not have a bank account, are managing someone else’s affairs, or do not have a permanent address can apply post.
It is also possible to call Social Security Scotland free on 0800 182 2222. Phone lines opened at 8am on Monday.
An automated message said the line was experiencing a high volume of applications for the Scottish Child Payment.
Monica Lennon, Labour MSP, said: “It’s no surprise that there’s a high level of demand for the Scottish Child Payment, given the rise of poverty and hardship in our communities.
“[The Scottish Government] must ensure the website and phone-lines can cope with the demand, because delays have consequences.”
A Social Security Scotland spokesperson said: “We’d like to apologise for the short time that the Scottish Child Payment online application was unavailable for this morning. The online form was back up and running by midday.
“We’d like to thank people for their patience while we worked to rectify this. We moved all available colleagues to take calls while we made sure that the online form was back up and running.
“The introduction or expansion of services is never without risks. We had staff on hand to monitor issues and to fix these quickly. This will continue throughout this week as we expect to see continued levels of high demand.”
The payment has been praised by anti-poverty charities.
The Joseph Rowntree Foundation said if the scheme was replicated across the rest of the UK 5.3 million youngsters in England, Wales and Northern Ireland could benefit.
Chris Birt, associate director for the think tank in Scotland, said the benefit should show the UK Government that “prioritising those on low incomes is possible”.
It also shows other devolved governments that the “constraints” on their powers are “no barrier to compassionate and significant action to support families”, he added.
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