Board members said such a big change affecting a community hub should not have been permitted before they had contributed input to the decision-making process.
"Moving the pedestrian crossing and removing these carparks will reduce safety and accessibility around this vital community hub," they said in a joint statement.
"These carparks are very important for families with young children, senior citizens and those with reduced mobility.
"They are on the flat, near the front door, and have provided safe access to this community hub for decades."
Port Otago chief executive Kevin Winders has cited safety as the principal reason for shifting the crossing along Beach St, away from the George St intersection.
This would result in eight carparks being lost immediately in front of the library.
NZ Transport Agency Waka Kotahi gave the green light to changing the roading layout.
Board chairwoman Ange McErlane said the community was "completely up in arms" and distressed.
Board members were angry about what they described as a fait accompli.
"Someone should have consulted us," Barbara Anderson said.
She wanted to know what evidence there was of a safety problem at the existing crossing and what options were looked into.
Wayne Sefton said it was difficult to be an effective elected representative "if no-one tells you what’s happening".
Duncan Eddy noted the library was part of a complex that was also a council service centre and town hall.
"Significant changes are being made without talking to the people who use it."
Reflecting on when her four children were younger, Kristina Goldsmith doubted she would have set foot in the library if the parks in front of it had not been there.
She was one board member worried about creation of a disincentive to use a community facility.
Jarrod Hodson doubted the wisdom of shifting a crossing closer to a railway line.
