The body responsible for running London Stadium spent £100,000 developing a communications strategy for the stadium despite having three senior communications staff paid more than £260,000 combined.
London Legacy Development Corporation (LLDC), which lost more than £20m last year, has been criticised for the way it spends taxpayers' cash.
But LLDC says the £100,000 helped to avoid higher costs down the line.
"This was a one-off project," it added.
The figure, from July 2018, is contained in detailed expenditure published by the LLDC. As a taxpayer-funded organisation, it has to publish details of all contracts in excess of £5,000.
LLDC also spent £4m on legal costs in an acrimonious dispute with the core tenant, Premier League side West Ham United.
That dispute was bought to an end minutes before a lengthy court case was due to begin on 12 December, when a deal was brokered between the club's managing director Karren Brady and LLDC chief executive Lyn Garner.
James Roberts, political director of lobby group the TaxPayers' Alliance, said: "You would have thought the LLDC would have been doing everything they could to keep costs to a minimum.
"Instead, their accounts show they've splashed taxpayers cash on expensive PR strategies and pointless wheezes like award ceremonies. Before kicking off again at West Ham about their costs, the LLDC really need to get their own house in order."
LLDC also spent £32,000 on "media planning and buying services" for its 2018 Queen Elizabeth Olympic Park summer campaign, while using the London Stadium and its catering and security facilities for last year's East Works Awards cost another £19,650.
An LLDC spokesman said: "The LLDC has a wide remit and responsibility and in line with similar organisations will buy in specialist services as required. All contracts over £5,000 are published and there is an audit and procurement process. The LLDC operates within its agreed annual budgets."
And on the £100,000 spent on an outside agency developing a communications strategy, it added: "Specialist research, stakeholder and communication advice was procured when the director of communication post was vacant during a time when multiple legal actions were under way against the London Stadium.
"This was a one-off project involving research and development and was part of the strategy which avoided a prolonged and expensive court case and provided information to inform the commercial strategy. There is no ongoing outside communication support."
London Stadium's owners E20, a wholly owned subsidiary of LLDC, reported losses of £22.7m in the year to 31 March 2018.
In a critical review of the stadium's finances in December 2017, London mayor Sadiq Khan said he would be taking control of the situation in a bid to reduce the losses.
London Stadium was built for the 2012 Olympics and has been dogged by controversy over its finances. Converting it into a football ground cost £323m when the original estimate was £190m.
