A man who wished to be buried next to his wife lay in the wrong grave for 10 years, a report found.
The couple's daughter bought two cemetery plots - with the intention of burying her parents on the sides they slept in bed - before the husband's death in 2008.
He was buried on the wrong side, but the error was not noticed until his wife's death in 2018.
Northampton Borough Council has apologised and paid £500 compensation.
The Local Government and Social Care Ombudsman said the plots in Kingsthorpe Cemetery were bought in 1999.
When her father died, funeral directors told the couple's daughter he would be buried in a plot, labelled Y in the report.
Having agreed he would be buried in a different plot - X - she queried this and the relevant paperwork was corrected, the report says.
Despite this, her father was buried in plot Y.
"No family members noticed the error as the graves either side were empty grassed areas," the report says.
Ten years later, when the mother died, the cemetery office noticed the error and informed the family, who agreed that the burial could take place in plot X.
The daughter said it was her understanding that land on the "correct" side could not be used for burials as it had subsided.
Afterwards, she registered a complaint, accusing the council of "covering up" its mistake.
It said the error had been genuine, but could not offer an explanation.
The council offered to exhume and rebury the woman's parents in the correct plots, but the ombudsman said the "family understandably felt this was too distressing and declined".
Their daughter, who did not wish to be named, said she felt "robbed" of telling her mother about the mistake while she was still alive.
"My mother suffered from Alzheimer's but if we'd have known this not long after my father had died, she was OK, we'd probably have accepted it as a family and it would not have been an issue," she said.
She said she had not been to the graves regularly since discovering the error because she "doesn't want to see" them.
This is not the first time that the same council has been involved in cases of wrongful burial - with two other cases in 2016.
A council spokesman said: "We have apologised unreservedly and have reviewed our processes to ensure that customers' wishes are gathered at the point of plot purchase to avoid any future misunderstandings."