The Birmingham Post (p3) reports that Peter McDonald was named by the town's Tory MP, Julie Kirkbride. She said it was clear Mr McDonald was responsible for obtaining names of pensioners who had free bus passes who were then contacted and told the Tories planned to abolish them.
The alleged incident happened during the hard-fought local election campaign in May, which saw the Conservatives regain the council from Labour.
Ms Kirkbride complained to the data protection registrar, who has started an investigation to see if there have been any criminal offences.
She quoted a letter from Mr Bryant which said the council's head of financial services, Andrew Fisher, first refused to provide the information. His letter said Mr Fisher was then subjected to 'considerable' pressure from Mr McDonald.
It went on: 'In eventually yeilding to that pressure, Mr Fisher told councillor MrDonald of his reservations in supplying the information and indicated that under no circumstances was it to be used for political purposes.
'In retrospect, and assuming the Labour Party are unable to offer an alternative version of events, it would appear that Mr Fisher's trust in councillor McDonald was misplaced.'
Mr McDonald refused to comment but West Midlands Labour Party regional director, Roy Kennedy, said: 'The Labour Party takes these matters very seriously indeed. We are acting swiftly in investigating these allegations. We will consider any action in the light of the investigation.'