Ealing Council is looking into allegations made by columnist Katie Hopkins that postal votes have been seen by a member of the public before the General Election.
Ms Hopkins posted a picture on Twitter of someone appearing to claim Ealing Central and Acton postal votes were not "looking good".
She told her 773,000 followers she had written to the council to complain, before claiming it replied an investigation had been launched.
The council said it had robust processes in place to ensure that postal votes remain confidential
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When Getwestlondon approached the council for comment, it said "appropriate action" was being taken.
The local authority said the individuals named by Ms Hopkins did not attend opening sessions for postal votes.
A spokesman for the Ealing Central and Acton returning officer, on behalf of the local authority, said: "No postal votes are counted until after polling closes on Thursday, 8 June.
"We have robust processes in place to ensure that postal votes remain confidential.
"When envelopes are opened the ballot paper is placed face down so that the vote is not seen and ballots are then placed in a ballot box, which is then sealed and stored securely until the poll closes.
"Accredited postal vote agents are entitled to attend and observe these opening sessions.
"We can confirm that neither of the individuals named in the tweet have attended any of our opening sessions.
"We treat all allegations of misconduct extremely seriously and are taking appropriate action.
"We were in contact with Ms Hopkins and asked her to share any information with us either in person or via email.
"She has provided a screen shot of a tweet being widely shared on social media yesterday.
"Everyone who attends these opening sessions is given a copy of the legal secrecy requirements and we are reminding them of their duty to maintain the secrecy of the ballot."
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