A Labour-organised festival dubbed "JezFest" did not make a profit, the party's treasurer has confirmed.
Diana Holland added, to applause from members, that she did not believe a desire to make money was the reason why Labour Live was organised.
More than 13,000 tickets were sold for the one-day June event in London which featured Labour leader Jeremy Corbyn and electropop band Clean Bandit.
But ticket prices were slashed to £10 from a high of £35 for adults in a bid to boost sales.
Johanna Baxter, a former member of the party's ruling National Executive Committee, asked how much the festival cost to organise, if a profit was made and whether it will be repeated.
Speaking at Labour's conference in Liverpool , Ms Holland replied: "No, Labour Live did not make a profit.
"I don't think that was why it was organised, however, there was a net cost. It'll be included in next year's financial report.
"But this was met by part of the reserve fund we have established in addition to the general election fund, so absolutely none of that was touched but we did use some of our reserves in order to fund that."
Theresa May earlier this year mocked Labour over the festival during Prime Minister's Questions.
She told MPs that shadow chancellor John McDonnell and the Magic Numbers were among those appearing at the event, adding: "Just about sums them up."
