Representatives from seven unions are involved in the negotiations, aimed at establishing a new enterprise bargaining agreement with the water company.

The Communication, Electrical and Plumbing union has accused the company of being "out of control and in need of leadership".

CEPU state organiser Todd Lambert said the company's behaviour had him "shaking his head".

"Someone needs to step in immediately to avoid a major industrial battle commencing," Mr Lambert said.

Mr Lambert claims TasWater has ignored a recommendation by Fair Work Australia and has not given reasons why it will not accept the union's proposals for work conditions put forward last month.

A spokesman for TasWater said the company had complied with the recommendations and would continue to do so.

"While we're disappointed with the CEPU's unilateral attempt to undermine this important process for our employees, we will continue to negotiate with the single bargaining unit in good faith," the spokesman said.

"We continue to brief our employees throughout this process in an open and transparent way as we have since the start of negotiations."

Employees had raised concerns over attempts to cut back their public holiday and annual leave entitlements following the merger of the three water companies.

"TasWater employees are only asking to keep what they already have in their agreements so they won't be disadvantaged through the merger," Mr Lambert said.