The eponymous charity that runs the school said that the event is "no longer viable in its current format", citing "increasing pressure on training budgets, particularly within local planning authorities".
It added: "Changing lifestyle and work patterns have meant a steady decline in attendance over previous years".
Summer school president Roger Pidgeon said: "The trustees of the Planning Summer School have carefully examined a range of options to continue to hold an annual school but have, with the greatest reluctance, concluded that in today’s market this type of event is no longer deliverable."
Pigeon’s immediate predecessor Leonora Rozee said: "I fully support the difficult decision of the trustees to formally end 80 years of the annual Planning Summer School event.
"It is a sad reflection of current cuts to the public purse that many local authorities are unable to support the CPD and training requirements of their professional staff and elected members."
The first Planning Summer School opened on 11 September 1933 at Digswell Park Conference House in Welwyn.
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