Two hundred email addresses were “inadvertently” sent by Fenland District Council of people who had responded to a consultation about growth and regeneration.
Residents who had shared their suggestions on the Fenland Local Plan via email were alerted to the blunder on February 5.
"This should not have happened and we sincerely apologise for the error," Gemma Wildman from the local plan team said.
"It has been brought to our attention that an error was made in the sending of a recent communication regarding the local plan.
"All email addresses were inadvertently included enabling all recipients to see all consultee email addresses.
"Only your email address has been shared, no other personal data has been disclosed, any personal risk to you is minimal."
The local plan team said the data protection officer had been informed and they were "in the process of reviewing practices to ensure that the risk of recurrence of such an error in the future is reduced".
One resident whose email address was included, who did not wish to be named, said they were "shocked" that the other recipients were not hidden.
In an anonymous email sent to the Cambs Times, they said: "I don't know if there were multiple batches of emails, but the one I received contained the email addresses of 200 consultation respondents."
The local plan focuses on policies and locations for the growth and regeneration of Fenland over the next 20 years.
The consultation took place over a six-week period from October to November 21 2019.
An online questionnaire could be filled out and returned by email or post.
Comments were helped to inform a draft local plan to be published for public consultation in summer this year.
A document issued on the local plan by FDC in October last year, read: "How we will protect your data all personal information that you provide will be used solely by Fenland District Council for the purpose of the consultation on the Fenland Local Plan.
"Please note that each comment and the name of the person who made the comment will be featured on our website - comments will not be confidential.
"Your views are essential at this early stage in helping to shape the growth of the district."
A spokesperson for Fenland District Council said: "We take the matter of data protection extremely seriously and therefore when we became aware of this issue we sent an email to all individuals and planning agents concerned, informing them of the error and issuing an apology.
"We have also made all staff aware of the need to ensure accuracy when sending emails to prevent an issue of this nature occurring again in the future.
"In addition we are also in the process of rolling out the Gov. Notify functionality across the organisation which allows bulk emails to be sent without the risk of recipient email addresses being inadvertently shared.
"Furthermore we have also self-referred this breach to the Information Commissioners Office."
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