James Prentice took his mum Laurietta to the Wollongong NSWTG office on January 15, 2016 to get her affairs in order. She was under heavy medication and in the care of a doctor and psychiatrist at the time.

Mrs Prentice went into an appointment room - alone as per normal practice - with a NSWTG employee and changed her Will.

But the only material change was the removal of her son and daughter as executors, with the NSWTG instead putting itself in the role.

Mrs Prentice, 91, died in June this year and the NSWTG is proposing to charge in excess of $24,000 plus other charges for the execution of a simple Will, as per law, when a solicitor's fees for the same service are legally capped at $6000 for Probate, with about $2000 to be expected for administration.

Mr Prentice has engaged a law firm to request NSWTG renounce its position as executor to his mother's will.

"We did not see a full disclosure of NSW Trustee and Guardians' executors' fees until our mother's passing," Mr Prentice said.

"When my mother walked out of her appointment we believed there was nothing to peruse, examine, or be fearful of.

"However, we were shocked to learn when we went into administration of the will that the executor had been changed and that the NSW Trustee and Guardian had taken over.

"And that's the luring effect of the 'free Will' ... you think where it started is where it ends, but it's not a free will at all, it has a hidden component in it to the benefit of the trustee, and we only found out about this component when our mother had passed.

"I think the actions of the NSW Trustee and Guardian are wrong, deceitful and unethical."

Attwood Marshall Lawyers Senior Associate, Lucy McPherson agrees and has called on the NSWTG to renounce as executor of the estate and to apologise to Mr Prentice and his family.

She also wants an investigation into their policy in relation to transparency and disclosure of fees.

"The deceased was 87-years-old, suffering hallucinations and cognitive decline when NSW Trustee and Guardian was appointed as executor of her Will," Ms McPherson said, adding the change was the only material amendment to her existing Will.

"For NSW Trustee and Guardian to be appointed as executor of Laurietta's will was entirely unnecessary and ill measured when considering the additional costs that would be incurred and because her two children, who were the executors of her prior Will, were entirely capable to act in that role," she said.

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"NSW Trustee and Guardian suggested they were appointed as executor with the knowledge there would be significant costs that would be incurred by the estate in doing so."

Ms McPherson said the NSWTG had an exorbitant and grossly unfair fee structure when acting as executor of an estate.

"In this matter the fee estimate for obtaining a grant of Probate and administering the estate was $24,000 plus monthly administration fees," she said.

The professional fees a solicitor is entitled to charge to obtain a grant of Probate is set by legislation.

For an estate of this size the costs for legal services for obtaining a grant of Probate are capped at $5,636.

"The fees are set out in a complex matrix and it is highly unlikely that an elderly, frail, vulnerable woman with impaired capacity would have been able to comprehend the fees to be charged when she appointed the NSW Trustee and Guardian as executor," Ms McPherson said.

"There is no evidence to suggest that the NSW Trustee and Guardian properly disclosed the fees at the time the will was made, and the fact they did this in circumstances where the deceased had impaired capacity is appalling.

"The conduct of the NSW Trustee and Guardian has caused the deceased's family significant heartache."

NSW Attorney General Mark Speakman said he was informed that NSWTG was "making progress to improve the quality and timeliness of the important services the organisation provides, in respect of some of the most vulnerable people in our community'.

"While it would be inappropriate for me to comment on the specific details of any individual case, I have been assured that the matter raised is being investigated," he told the Mercury. "I expect the NSWTG to address the allegations and to ensure that its practices meet community expectations."

Mr Prentice said he and his family had been devastated by the ordeal.

"The actions of the NSW Trustee and Guardian are wrong, deceitful and unethical," he said.

"I think it's a worrying situation to be taking advantage of our family like that.

"The word 'trust' has gone out the window, it's a fallacy, and they have no right to act in this way when wills and estates lawyers have to comply with strict rules and regulations.

"Even if my mother had been informed of the fees or the change in the role of the executor, she was incapable of understanding the complicated fee structure of NSW Trustee and Guardian because of her psychological state and deteriorating health," he said.

"We want them to acknowledge the wrong in all of this, to demonstrate to the community that they have ethics and to stop doing this to vulnerable people because it rips into the soul and goodwill of affected families," he said.

A NSW Trustee and Guardian spokeswoman said the government agency does not comment on individual cases.

"Any information pertaining to the drafting of a Will or the administration of an estate is subject to privacy laws and the common law duty of confidentiality," she said.

When NSW Trustee and Guardian makes a Will for a customer, part of the interview process includes a capacity check.

"All NSW Trustee & Guardian Will makers are trained in accordance with the legal test for capacity in relation to making a Will," the spokeswoman said.

The fees to administer an estate is explained to a customer at the time they make their appointment for their Will.

"When the customer comes in for their appointment the Will maker at the beginning of the interview takes the customer through what the fees are for NSW Trustee and Guardian to administer the estate."

Towards the end of the interview the Will maker prepares an acknowledgement of advice.