Sainsbury's chairman David Tyler has been fined by the retailer's board, after he was found to have used the supermarket's staff and suppliers to work on his country retreat in East Sussex.
Following an investigation over the events, which took place in 2013, Tyler, who has held his role at the FTSE 100-listed giant since 2009, received a written warning by the supermarket's board and paid £5,000 ($6, 225, €5,800) to charity in recognition of the work carried out by the staff.
However, the company said the investigation, which was led by Sainsbury's non-executive directors Mary Harris and Gary Hughes, found Tyler's actions did not result in financial gains.
"The chairman volunteered the information and the board conducted a thorough investigation in line with company policy, as they would with any other colleague in the same circumstances," the firm said in a statement.
"As a result of the investigation, the chairman was given a warning but the board concluded that his failure to comply with company policy was unintentional, that he did not act dishonestly and made no financial gain."
According to documents seen by the Guardian, Tyler was found to have used the services of a member of Sainsbury's sustainability team over his plans for underfloor heating systems at the property.
The employee, who had expertise in green energy and engineering, paid numerous visits to the property during his working hours and spoke to a Sainsbury's building contractor to develop a plan for the property.
The firm did so without charging Tyler, before installing an oil-fired boiler at his house, a process worth £10,000 according to the investigation.
Tyler, who asked another employee to assess insulation at the property, is also understood to have contacted two specialist advisers over alternative fuel sources.
The Sainsbury's chairman, who was paid £496,000 last year and holds the same role for Hammerson, the listed shopping centre developer, was found to have breached the company's ethical supplier guidelines over a conflict of interest.
According to the FTSE 100-giant's policy, being directly involved in a personal or business relationship with a colleague, competitor or supplier "could affect or compromise what you do at work".
Tyler breached the policy after failing to disclose his relationship with suppliers and staff members, as well as receiving advice from personnel he was not authorised to speak to in a personal capacity.
"He received (paid-for) services from an expert supplier due to his position that he would otherwise not have been able to," the report added.