Sunderland International Airshow cost almost £120,000 more to put on than expected last year.
Council cabinet papers show that £252,000 was spent on the popular event – which attracts around one million visitors to the city – but its intended budget was just £133,000.
The £119,000 overspend means that tourism chiefs will look at “options for further income generation and the scope of the event will be examined as part of next year’s programme”.
The Airshow is the biggest event held in Sunderland each year, attracting huge crowds to the city’s seafront to see thrilling displays and performances.
Meanwhile, Sunderland Live, the council-funded company which organises the air show as well as being involved with other big events including Sunderland Illuminations, is set to report a deficit of more than £430,000 this year.
Council bosses have defended the figures, saying Sunderland Live has delivered “high-quality events” for the city which has significantly boosted its economy.
Sunderland Live has also been given a reduced management fee of £650,000 from the council for 2017/18.
The cabinet report read: “The company has not been able to constrain expenditure within the commissioned budget, and will be reporting an in-year deficit of £434,000.
“The way in which core and community events are delivered in the future are being reviewed in order to inform future programmes.
“These pressures will be met from contingencies in the current financial year at outturn.”
Coun Robert Oliver, of the city’s Conservative group, said: “The figures are alarming as they come at a time when Labour councillors are complaining about cuts from the Government but are tolerating too many loss-making local interests which are a drain on the Council Tax.
“Sunderland Live must at least break even and preferably make a surplus which can be used to support future events in the city and this could be done by increasing sponsorship of events or introducing small admission charges.
“A £1 charge was introduced to enter Roker Park during the illuminations and this could be done at restricted areas of the airshow as it would still allow general entry and local residents to get home.
“With the airshow bringing in £12million to the regional economy last year there is also an opportunity to ask private businesses which benefit from increased visitor numbers to sponsor and support the event rather than the local taxpayer.
“Durham Council has attracted funding from the Arts Council for Lumiere and there is no reason why Sunderland should not also be able to do the same so that the events are sustainable and preferably bring in revenue for the city.”
Wearside Liberal Dem councillor Niall Hodson slammed the figures, saying: “Once again we see that Labour councillors in charge of Sunderland Council - who claim that they don’t have enough money to spend on basic services like libraries or cleaning our streets - don’t seem to have a grip on the council’s finances.
“Before they go ahead and cut vital services, ruling councillors must end their wasteful spending.
“When it comes to the Airshow, perhaps if the Labour cabinet stopped spending taxpayers money on a VIP marquee for councillors and their guests they might not ‘overspend’ so much.”
Councillor John Kelly, portfolio holder for culture, said: “Sunderland Live has delivered a number of high quality events in the Sunderland area that have attracted thousands of visitors and contributed to the local economy.
“The council will be further reviewing the amount spent on events as part of its financial plans for 2017/18 onwards.”