The Sydney Gay and Lesbian Mardi Gras has apologised after thousands of ticketholders were forced to miss the headline acts at the official afterparty due to the venue reaching capacity.

Key points: The Hordern Pavilion has a capacity of 5,500 but more than 10,000 tickets to the official afterparty were sold

The Hordern Pavilion has a capacity of 5,500 but more than 10,000 tickets to the official afterparty were sold Many people queued for hours and still did not get to see any of the headline acts

Many people queued for hours and still did not get to see any of the headline acts Mardi Gras organisers said space was limited because the Royal Hall of Industries was unavailable

Many attendees on Sunday complained the organisation oversold the event for profit, and pledged they would not attend in future years.

Tickets to Saturday's post-parade event at the Hordern Pavilion in the Moore Park Entertainment Quarter cost between $200 and $270.

Organisers secured what they said was the "holy trinity" of performers, with international acts Dua Lipa, Sam Smith and Kesha topping the bill.

But thousands of people were stuck in queues that snaked around the Hordern Pavilion as the venue hit capacity before any of the performers took to the stage.

The space can hold 5,500 people but about 10,000 tickets to the party were sold.

Many ticketholders used social media to complain and demand refunds.

"The event organisers for the afterparty failed miserably. The line-up to get into the pavilion didn't move all night, with thousands outside who paid (around $200) for a ticket to watch performances on tv screens," Sara Stevens wrote on Facebook.

"Either reduce ticket numbers or get a bigger venue … it was crap and poorly managed."

Mardi Gras organisers have acknowledged changes must be made so the party is successful. ( ABC News: Paige Cockburn )

Others said they were embarrassed many international visitors experienced such a "disappointing" Mardi Gras event.

"Mardi Gras has lost its soul to money," Kenneth Bryan said on the organisation's Facebook page.

The Sydney Gay and Lesbian Mardi Gras (SGLMG) warned attendees there would be challenges accommodating partygoers because the Royal Industries Hall, also in the Entertainment Quarter, was not available this year.

The Hordern Pavilion and RIH are under lease by the PlayOn Group, a partnership between Playbill Venues and the Sydney Swans, and the RIH is closed for redevelopment.

In a statement on Sunday afternoon, SGLMG said other venues across the city were considered but it was determined that the Hordern Pavilion and its surrounding areas were still the most suitable.

"There just isn't another inner-city space that is big enough for our audience that would allow an all-night dance party," the statement read.

The SGLMG said screens were set up outside so revellers who were not lucky enough to make it inside the pavilion could still watch the performances.

However, the organisation acknowledged many spent much of their night waiting.

"We are deeply disappointed and apologise this has occurred," it said.

"We recognise significant changes are required for the smaller party footprint to be successful."

A spokesperson for SGLMG told the ABC he could not comment on whether or not refunds would be considered.