Longer freight routes between the islands and through the northern South Island have prompted freight company Toll NZ to hike its rates.

This month's 7.8 earthquake near Kaikoura, which demolished State Highway 1 and the parallel rail link past Kaikoura, has resulted in a scramble by all freight movers to re-route freight by road and ship.

The inland Christchurch to Picton route is hundreds of kilometres longer and has been estimated by industry associations to add about 20 per cent to costs.

In a letter to customers obtained by the Otago Daily Times, Toll, New Zealand's largest domestic freight forwarder, said the company was incurring "considerable additional costs".

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These were unavoidable, said Toll Group New Zealand's business development and sales general manager Roberto Brady.

"We seek your understanding with the resulting surcharge we have to apply to all Interisland and also Intra-Island for Marlborough Freight Forwarding consignments from Monday 14 November to cover these costs," he said in the letter.

For northbound South Island freight, Toll has added a 10 per cent surcharge. Southbound freight costs from Auckland and Northland have incurred a 19 per cent surcharge, while 25 per cent more has been charged on southbound freight from Waikato, Bay of Plenty, Taranaki, Hawke's Bay, Manawatu, Wairarapa, Wellington and Marlborough.

In Wellington, CentrePort's two gantry cranes and container berth remain out of action but container ships with their own on-board cranes will start moving cargoes today.

CentrePort chief executive Derek Nind said other short and medium-term solutions included using mobile cranes on the wharf, and possibly adding a purpose-built platform to support the gantry cranes.

Brady said the "significant disruption" from the quake meant alternate routes and extra equipment and labour were required to move freight between the islands and through the northern South Island. He said the Lewis Pass route added a deviation of 286km and Arthur's Pass 586km.

Toll had mobilised more trucks on the North and South Island line-haul routes, was transferring cargoes in and out of Christchurch from rail to road, and planned to introduce greater coastal shipping capability.