An email was sent to NTUC leaders and members on Saturday (19 May), asking them to complete the survey.
The poll asked questions such as which speech during the parliamentary debate was most memorable and how participants came to know about the debate.
This is the second time that a NTUC survey has been leaked in recent months.
In March, another NTUC survey on the raising of GST was leaked.
The survey was conducted in Nov 2017, prior to Budget 2018 in Feb this year, leading to concerns that the results would be presented to the government as a gauge of public sentiment.
NTUC denied that results of the 440 responses was presented to the government.