One of the most senior civil servants in the Department for Work and Pensions (DWP) has placed the blame for the carer’s allowance benefits crisis on victims, many of who have been left with life-changing debts.

In an internal blogpost written for Whitehall colleagues, Neil Couling, the director general of DWP services, said individual failings by carers were “at the heart” of the issue that has been likened to the Post Office Horizon scandal.

The post, which was removed after the Guardian made inquiries about its content, has been met with outcry by charities and politicians.

An independent review into the scandal last month found that longstanding and “unacceptable” systemic DWP leadership problems and poor benefit design were at the root of the failure, which it said could not be blamed on carers.

Some carers who fell foul of the benefit’s outdated and complex rules felt so shamed, distressed and desperate they contemplated suicide, the review found. It described being caught in the system as like being “at the whim of a faceless machine”.

The review, by the disability rights expert Liz Sayce, concluded that senior DWP leaders had for a decade failed to grip or fix problems with the benefit, despite repeated warnings by whistleblowers, auditors and MPs.

Couling’s post said one of the main causes of overpayments was as a result of the DWP’s “rather byzantine” guidance on the averaging of carer’s earnings. But he suggests these overpayments ultimately occurred because individual carers failed to report fluctuations in their earnings that breached benefit rules.

“Incidentally what has been missed in all the [media] coverage is that this error (and hands up we made it and we will put it right) affects only a relatively small number of cases and wasn’t the cause of the original complaint. Because at the heart of the overpayment issues in CA [carer’s allowance] is a failure to report changes of circumstances,” Couling wrote.

This is at odds with the government’s own position, which accepts the DWP itself was the main cause of overpayments because of its confusing guidance and unclear reporting processes.

Kirsty McHugh, the chief executive of Carers Trust, said: “This seems to be a really serious error of judgment. There has been an independent review which came up with some very clear findings. The DWP must now stand by this report and get on with returning money to carers.”

The Liberal Democrat leader, Sir Ed Davey, said: “I’m disgusted by this blogpost as it shows some senior DWP people have learned nothing about the scale of the misery their policies and procedures inflicted. It’s high time the DWP showed some respect to carers and some awareness of their own gross errors.”

Emily Holzhausen, the director of policy at Carers UK, said: “To say that the heart of the matter is claimants’ fault for not reporting changes in circumstances is missing the point entirely. The root cause of this is a confusing, complex and difficult to navigate system, which has caused numerous errors.”

The government-commissioned Sayce review was ordered after an award-winning Guardian investigation revealed how unpaid carers had been unfairly hit with draconian penalties of as much as £20,000 after unwittingly running up overpayments of carer’s allowance benefit.

The government announced in response to the review last month it would reassess some overpayments issued to carers during the past 10 years. It estimates about 200,000 cases will be reviewed, with 26,000 likely to have debts cancelled or reduced.

Last week, Sir Peter Schofield apologised to MPs for what ministers have called a “mess” inherited from the previous government: “I am sorry for all of those who are affected by this, but I am going to sort it out,” Schofield said.

Six years ago, Schofield refused three times to apologise to MPs over carer’s allowance failures. Although he then promised to fix the overpayment problem, 180,000 carers ran up debts of £300m on his watch between 2019 and 2025, roughly one in five of all claimants, of whom 854 were convicted of fraud.

A DWP spokesperson said: “We have been clear, and remain of the view, that we accept the vast majority of recommendations put forward in the Sayce review, including that confusing rules on averaging earnings left carers facing unexpected debts.

“That’s why we are tackling this issue and have already put in place extra staff to prevent carers building up large debts, updated internal guidance, and ensure letters to unpaid carers clearly explain what changes need reporting.

“And we will continue putting things right and rebuilding trust by reassessing affected cases, and potentially reducing, cancelling or refunding debts for tens of thousands of carers.”