Isle of Man Post says it was disappointed to receive a petition of 'no confidence' in the board and its chairman, Pam Crowe, MLC.
A twelve page document, sent to all 24 members of the House of Keys, contains 195 signatures of local members of the Communication Workers' Union.
Vice-Chairman of the board Geoff Corkish, MHK (pictured), told Manx Radio he thought it was 'a little discourteous' of the union not to send a copy of the letter to Mrs Crowe.
However, he confirmed talks, over pension rights for future employees, were continuing:
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