"This year, because another subsidiary of Fletcher Building (Fletcher Residential) was announced last week as the preferred tenderer for a major residential development of the North and East Frame, there has been disquiet from a recipient of my invitation to drinks ahead of the All Blacks versus Argentina test," he writes.
"That person was part of a consortium that unsuccessfully tendered to develop the North and East Frame."
Mr Brownlee refuted suggestions that Fletcher Construction's sponsorship of the event could influence any tender process a subsidiary of Fletcher Building might participate in.
"This is not the first time conspiracy theorists have tried to suggest something along these lines," he added.
"Personal attacks of this nature, without foundation, and as a kneejerk reaction to non-selection as a preferred tenderer, is extremely disappointing."
The media drinks, which has never had taxpayer money spent on it, was first held in 2012 when Christchurch hosted the All Blacks vs Ireland - the first major sporting event for the city after the devastating quakes.
It was held to show international and domestic media visiting the city that it was still capable of hosting major events, Mr Brownlee said.
"The last thing we wanted was foreign visitors who would be reporting back to their home countries not knowing where to go to get a meal or a drink, and getting a poor impression of the city and its fledgling recovery and rebuild process," he said.
Fletcher Construction sponsored the inaugural event, which Mr Brownlee said was a "huge success, with visiting media rubbing shoulders with local media, those involved in the rebuild from many organisations, and rugby players past and present".
A clearly disappointed Mr Brownlee apologised for the cancellation of next Thursday's function.
"There is much to celebrate in how far we've come since the Canterbury earthquakes," he wrote.
"Unfortunately we won't be discussing it over a drink ahead of next week's test match.
"The potential for reputation damage to Cera, myself and Fletcher Construction is just not worth it."