Ten thousand free tickets for a special celebration of the Queen's Diamond Jubilee at Stormont were snapped up in six minutes on Tuesday.
The event will take place next Wednesday as part of a two-day visit to Northern Ireland by the Queen.
An additional 10,000 tickets were distributed to invited guests from groups including youth organisations and the health sector.
But there were complaints from disappointed members of the public, particularly after it emerged that hundreds of tickets had gone to politicians.
The Northern Ireland Office, which organised the event, said: "We welcome the interest in the Queen's visit and the Diamond Jubilee celebration in the grounds of the Stormont estate in Belfast.
"Ten thousand tickets were offered free of charge this morning and were taken up in six minutes. Tickets were limited to five per person to allow as many families as possible to attend.
"We recognise a number of people may be disappointed, and we are examining with the Stormont estate authorities and the PSNI (Police Service of Northern Ireland) whether there is scope for any additional allocation of tickets, but there will be health and safety constraints."
The Queen is set to visit Belfast and Enniskillen during her trip, but the Stormont event has attracted major publicity.
Leader of the Traditional Unionist Voice Party Jim Allister called for further information on how the tickets for the Stormont event were distributed. After members of the Northern Ireland Assembly said they were each entitled to at least four tickets, he added: "The distribution of tickets for this event should not be an occasion for patronage by politicians."
Last week it emerged that the nationalist SDLP had advised its elected representatives to apply for their allocation of tickets with the intention of passing them on to members of Stormont staff who may wish to attend the celebration.