"AICC has expelled him for six years for anti-party activities. We were asked by the party high command to announce the decision," Sinha told reporters.
He said the AICC had earlier served a show cause notice to Barman, but he did not reply to it.
Barman, who was the state Congress chief for three years and chief minister for one year (1992-93), attended some public meetings of Trinamool Congress last year.
At one such meeting, he had also shared dais with TMC supremo and West Bengal Chief Minister Mamata Barnerjee.
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