Parents who complained about "disturbingly poor" special educational needs supplies were reportedly monitored by their local council.
Online campaigners who were allegedly part of a parent carer group were accused of creating anonymous social media accounts to criticise the council's provisions.
In an attempt to link these accounts to the parents, Bristol City Council officials put together files of personal information obtained online.
One message reportedly showed a worker explaining how they used wedding photographs on Facebook to identify a parent.
The council alleges that concerns were raised by the Bristol Parent Carers Forum (BPCF) in October last year over members carrying out "conflicting" lobbying activities - a claim that BPCF denies.
An email seen by the Mail on Sunday said colleagues were "working hard to uncover concrete evidence" on the campaigners.
A parent expressed their shock over the council's surveillance, saying: "There has been a long history of parents being criticised and of an adversarial narrative being created that SEND is somehow a drain on the system."
In November 2019, an Ofsted report said the area's special educational needs provisions were "disturbingly poor".
In areas for development, it stated at the time: "Many parents and carers lack confidence in the local area and its ability to do anything for them or their children.
"This is reflected in the increased level of complaints. They do not feel their voices are heard or their views acted on."
Green councillor Christine Townsend said the element of trust has been "broken" with the council, which is headed by Labour Mayor Marvin Rees.
She added: "We don't know how many parents they have been looking at, what they were looking for and what they were doing with it."
Bristol City Council said the criticism seemed in conflict with the parents "representing the (BPCF) forum at strategic meetings as part of the SEND improvement partnership".
A spokesperson said: “We received an email from Bristol Parent Carers Forum (BPCF) on 7 October 2021, requesting that Bristol City Council (BCC) supply evidence to substantiate concerns that members of BPCF were carrying out online campaigning and lobbying activities which seemed in conflict with them representing the forum at strategic meetings as part of the SEND improvement partnership.
"BCC accessed BCC-administrated and publicly available social media pages in order to supply the relevant information to BPCF as requested.
“A fact-finding report to the Overview and Scrutiny Management Board (OSMB) was commissioned following concerns raised about the viewing and sharing of publicly available social media posts of BPCF members.
"The report will be sent to OSMB when it is completed."
The BPCF has denied that it asked the council to collect data about parents and carers of children with special educational needs.
In a statement, the group said: "In January 2022 new forum officers were elected and over the last 6 months, we have been working to strengthen our relationship with strategic partners and the wider SEND community groups in Bristol.
"Our aim as an organisation is to focus on working with our strategic partners and wider SEND community groups in Bristol to amplify and represent the voices of some of the most vulnerable people in our society and we will continue to this commitment."
