A midwifery regulator spent £240,000 on lawyers to redact information from documents it held on a grieving father.
The Nursing and Midwifery Council (NMC) spent the sum before it would release the documents to James Titcombe under the Data Protection Act.
They reveal the NMC collected information on Mr Titcombe's fight for an investigation into his son's death, including keeping an eye on his Twitter feed.
Mr Titcombe's son Joshua died after suffering pneumococcal septicaemia and a lung haemorrhage on November 5 2008, nine days after he was born at Furness General Hospital in Cumbria.
An inquest in 2011 heard midwives repeatedly missed chances to spot and treat a serious infection which led to his death.
And an inquiry found a "lethal mix'' of failures at the University Hospitals of Morecambe Bay NHS Foundation Trust led to the unnecessary deaths of 11 babies and one mother between 2004 and 2013.
Midwife Lindsey Biggs was struck off for failing in her duty of care to Joshua, while another midwife, Holly Parkinson, was suspended for nine months.
Some of the A4-sized reports sent to Mr Titcombe by the NMC had all but 10 words removed, the i newspaper reported.
One email with the subject heading "Twitter chat - key points" said "keep an eye on his feed".
Mr Titcombe also requested how much had been spent by the NMC on issuing the documents to him.
The NMC replied: "I am sorry you do not feel we have been transparent in the way we handled your data subject access request.
"As you know we engaged the law firm Fieldfisher LLP to help us deal with your request and the estimated cost of their work is £239,871.85 (including VAT)."
The legal bill is equal to the annual registration fees of 2,000 NMC members.
Mr Titcombe told the i: "The NMC has a remit to protect mothers and babies which sadly, following my son's death in 2008, they have woefully failed to do.
"However, when it comes to protecting their own reputation, clearly no effort and expense is spared.
"This is a shocking amount of money to spend on hiding information and I can only imagine how staff whose registration fees have paid for this must feel.
"This is the latest in a long running pattern of behaviour in which the NMC seem to be going to extraordinary lengths to defend the indefensible rather than adopting an open and honest approach to learn from the past."
An NMC spokeswoman said that due to the size of Mr Titcombe's request, it decided to seek help from a legal firm.
"This request involved information relating to multiple fitness to practise cases over a long period of time and each document needed to be read to ensure that we did not disclose any personal data relating to other individuals.
"We did not have the internal capacity required to respond to Mr Titcombe, which is why we had to take the decision to get help from an external company.
"We engaged an external company to help ensure that we met our obligations fully in an open and transparent way.
"Handling the request in this way has incurred a significant cost to the NMC, however, we believe that the approach taken was the best way of ensuring a full response.
"As part of this process the NMC provided a significant number of documents to Mr Titcombe.
"Within these documents there were a small number of cases where staff should have worded their communication more carefully and we apologise to Mr Titcombe for this."