Canberra centenary organisers have apologised for the long queues at food and drink vendors at the Lake Burley Griffin bash after a flood of complaints that the event was under-catered.

Canberra centenary executive director Jeremy Lasek said organisers tried unsuccessfully to attract commercial caterers to the event, putting the catering contract out to tender three times.

At one point, the centenary committee contacted 21 individual catering companies both in Canberra and interstate and still failed to find an operator prepared to take on the event. Organisers eventually approached Floriade caterer the Gema Group, which accepted the contract.

While the community's response to Monday's celebrations has been largely positive, the short supply of food and drink has been harshly criticised.

Estimates put Monday's crowd at about 150,000 and yet there

were only a handful of vendors, leading to excruciating waits of up to an hour for guests, many of them families with young children.

''Primarily, in broadest possible terms, there wasn't enough food, resulting in very long queues,'' Mr Lasek said.

''Particularly in the peak period in the afternoon, there wasn't enough food. There was a stampede about 3-4pm for ice-creams.

''Clearly, we apologise to people who found themselves stuck in a queue on a hot day.

''Nothing's worse.''

Mr Lasek said problems began last August when the contract was first put out to tender. Despite contacting 21 companies individually, there had been no expressions of interest when the tender closed.

''In the end we went to tender three times and we kept adjusting the scope of the tender to make it, pardon the pun, more palatable,'' Mr Lasek said.

Mr Lasek said companies might have considered the centenary bash to be too much of a risk because it was ''a new event'' running at the same time of year as tried and tested functions including the races, football and Enlighten.

''For some it may have been the size of the site that scared people off. People in catering like to know what they're dealing with.

''They're used to footy and racing events, so when we said we're going to have a big party around the lake people didn't see that it could be a big hit and huge money spinner.''

Mr Lasek said organisers advised the Gema Group to prepare for a crowd of ''up to 100,000'' but the company ''made their own judgment, which was below that''.

''We've had some complaints but overwhelmingly the feedback [about the day] has been positive. There were 1000 elements to the event and perhaps half a dozen didn't work as well as we would have liked.''

Attempts were made to contact the Gema Group for comment.