Official reports and private emails obtained by The Age show a key objective of the $6-million-a-year campaigns is to ‘‘position the Victorian Government as leaders in planning and managing water resources effectively’’.

A 14-page Government assessment of the 2007-08 Our Water Our Future ‘‘behavioural change campaign’’ says a central message of the TV, radio, newspaper and online advertisements is that ‘‘the Victorian Government is leading the nation with water reform to ensure sustainable water supplies for now and for the future’’.

An internal briefing note for water bureaucrats says the campaigns — which include the Target 155 push to encourage people to cut their water use to less than 155 litres a day — are designed in part to ‘‘share information on the Government’s plans and progress’’.

An email exchange last December between officials involved in organising the campaigns shows a Department of Sustainability and Environment officer saying to a Melbourne Water insider: ‘‘I will pretend to be wise and knowledgeable about behavioural change programs with a political bent.’’

The revelation that the campaigns — funded by Melbourne’s four main water companies with money raised from household and industry water bills — have a political purpose comes as water policy shapes as a key divide between the Government and Opposition in the lead-up to next year’s state election.

With Melbourne’s reservoirs at dangerously low levels, the Opposition accuses the 10-year-old Government of mishandling water supplies and failing to plan properly for future needs.

Labor argues its major water projects, including a controversial desalination plant on the Bass Coast and a pipeline to bring water to Melbourne from northern Victoria, will help ‘‘drought proof’’ Melbourne.