Councillors in York, who ignored the advice of their own experts to block a solicitor's bid for planning permission, have cost the authority £18,000.
A lengthy planning wrangle over the height of solicitor Simon Morgan's luxury home in Upper Poppleton ended in victory for the lawyer earlier this year.
A Government planning inspector at a public inquiry held in May ruled that York House, in Hodgson Lane, could remain unchanged despite it having been built 1.6 metres higher than the original permission allowed.
Before the inquiry Mr Morgan called for last-minute talks with City of York Council to avoid the costly legal battle. He said he would much rather see the money spent on cash-strapped council services.
But his plea fell on deaf ears and, as he predicted, the authority was hit with a hefty bill.
In his inquiry report, planning inspector Philip Asquith said: "The council acted unreasonably. I consider that a full award of costs is justified."
The details of the payout are revealed in a report to the council's planning committee, which meets on Thursday.
Members are asked to note the £18,000 costs awarded against the authority and authorise the sum, which has already been paid, to be met from the income from planning applications.
They are also asked to note the criteria in which costs can be awarded against the council.
The report to the committee says the authority "failed to provide evidence, on planning grounds, to substantiate each of their reasons for refusing planning permission ... or to demonstrate that they had reasonable grounds for considering it expedient to issue an enforcement notice."
Mr Morgan has always maintained the fact that his house was higher than original planning permission allowed had been the fault of a project manager who worked on it.
He had been invited to put in a bid for retrospective planning permission to regularise the breach, but, in a shock move in December last year, members of the council's planning sub-committee voted five-four to reject it, against the advice of their officers and the authority's barrister.
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