Two middle-aged brothers have been censured after a judge was told that they treated a sick elderly aunt's money as "their own private bank".
The 86-year-old woman, who has dementia and lives in a care home, gave her nephews the power to act as her attorney seven years ago, Judge Denzil Lush was told.
But a local authority with responsibility for the pensioner's welfare raised concerns about the way the woman's finances were being handled and an investigation was launched.
Detail of the case has emerged in a written ruling by the judge following a hearing in Court of Protection - which handles cases involving sick and vulnerable people - in London.
Judge Lush concluded that the two men breached their fiduciary duties and revoked their power to act as the pensioner's attorney.
The judge did not identify any of the people involved.
But he named the local authority with responsibility for the welfare of the pensioner as the London Borough of Brent.
The pensioner was born in County Cavan, Ireland, and moved to England in her 30s. She lives in a care
home in Kingsbury, north west London, he said.
A lawyer representing Brent council had told the court that the pensioner's funds had been "substantially dissipated" and the that pensioner had not had enough to pay care bills.
Barrister Christine Cooper had added: "What is clear, even on their own case, is that the (nephews) treated (the pensioner's) funds as their own private bank and doled them out to members of the family until they reached the point where she was unable to pay for the care she needs."
Judge Lush was told that the two men had: given £15,000 of the pensioner's money to their mother to "purchase a car"; loaned another brother a total of £50,000 to "assist" him in buying a new property when his current property was on the market; failed to explain withdrawals from the pensioner's
account totalling more than £60,000.
He also heard that the two men had sold a flat the pensioner had owned in Cricklewood, north-west London, to their sister for £200,000 - £30,000 less that the property had been valued at by estate agents.
The nephews had argued that the it was in the pensioner's best interests for them to retain a power of attorney.
They said they would be happy to submit accounts and agree not to take decisions concerning sums over a specified amount.
Judge Lush concluded that they were "unsuitable" and revoked their power of attorney.
He said they had contravened their authority, not behaved in the pensioner's best interests and "made a hash" of managing and administering her money.
"There has been an intermingling of funds, and the (nephews) have consistently given priority to their own interests and those of other family members over the interests of (the pensioner)," he said.
"(They) exceeded their authority in terms of the gifts they made."
He added: "(They) have breached their fiduciary duties in several ways and in the circumstances I am satisfied that they are unsuitable to be (the pensioner's) attorneys, and I shall revoke the (power of attorney)."
The judge said Brent council should take control of the pensioner's finances.