Unions are pushing for the Christchurch City Council to renegotiate its Cost Share Agreement with the Crown in a last ditch bid to stop assets being sold off.

Addressing the council on the first day of hearings on the draft Long Term Plan, Unions Canterbury said it was totally opposed to the council's proposal to raise up to $750 million through the partial sale of council-owned commercial companies such as the Lyttelton Port and Christchurch International Airport Ltd to strategic partners.

The organisation, which represents around 50,000 workers, said the council should re-open discussions with the Government over the Cost Sharing Agreement because the current deal was unfair and forced the council into paying for anchor projects most Christchurch people would be happy to defer or abandon.

"The Cost Share Agreement signed off by the previous council had behind it no public consultation or input whatsoever. Alarmingly the CCC is now locked into a huge capital programme that has inherent risk such as rising construction costs and completion date over-runes," it submitted.

"Given the uncertainties of such a large programme it would be foolish to commit at an early stage to sales of assets that may well be regretted later but turn out to be unnecessary financially."

The Rail and Maritime Transport Union told the council it was vehemently opposed to the proposed asset sales and viewed it as matter of life and death.

"In our experience the privatisation of publicly owned assets that are operated as businesses leads to a deterioration of health and safety standards and increased risk of serious harm and death. This was our experience during the privatisation of the rail industry in New Zealand," spokesman John Kerr said.

Lyttelton Port had an unhappy recent history of deaths and serious harm injuries on the waterfront and its inland port. The union did not wish the situation to be made worse by a sell-off of the port and would fight to stop any sale.

"We are urging you and pleading with you not to sell off the port," Kerr said.

The Christchurch Central/South branch of the Labour Party said rather than selling assets the council should be giving priority to drastically reducing its proposed capital expenditure and seeking to renegotiate the number, size and timing of the Government's "wish list" projects.

The council did receive support for the proposed asset sell-off from the Canterbury Employers' Chamber of Commerce.

Chief executive Peter Townsend said realising cash from assets sales and introducing strategic equity partners that could drive value into the community through the operation of those assets was critical to the future of the city.

"We are unashamedly emphasising the sale of assets to realise capital ... so we don't have to sweat assets, so we don't have unsustainable rate increases," Townsend said.

The New Zealand Manufacturers and Exporters Association (NZMEA) also supported the proposed asset sell-down, but raised concerns about the "excessive" level of rate increases the council was proposing. It said its businesses were already struggling to absorb rising costs and could ill-afford rate increases of the levels proposed.

If the plan was approved, there was a risk some manufacturers would quit the city, its spokesman Peter Suckling warned.