The website for pre-registering Mighty River shares was under pressure late into the night yesterday, as Kiwis rushed to get information about the sale.

According to the Treasury, which is overseeing the partial sell-down, there had been 92,959 pre-registrations by 11:15pm yesterday. Officials expect the figure will have hit 100,000 this morning.

Traffic to the website www.mightyrivershares.govt.nz was so heavy yesterday that the website struggled to cope with the volume.

Treasury had increased the capacity of the website to cope with the volume, with up to five registrations a second yesterday afternoon.

John Crawford, the Treasury's head of commercial transactions, said the website had taken more than 70,000 registrations of interest by 8pm last night, only around an hour after television advertising of the offer was launched.

''We're certainly pleasantly surprised on the upside,'' Crawford said.

''The world's changes in terms of media and how people respond quickly...The vast majority of those pre-registrations were driven only by online news channels.''

In the coming days officials would start to receive information on what amounts people had indicated they were willing to invest, but the immediate priority had been on launching the advertising, Crawford said.

Another rush of pre-registrations was expected just prior to that stage closing on March 22.

The frenzy came after the Government said that Kiwis who pre-register for shares would have their applications scaled back by less than those who haven't.While New Zealand investors are guaranteed at least $2000 worth of shares, in the event that those who want more are scaled back because of demand, those who pre-register will get 25 per cent more than those who apply for shares once the offer is already open.

A spokeswoman for Finance Bill English said yesterday that ''while there is an incentive to pre-register, there's no extra advantage in doing so today.
People have until 22 March to pre-register.''

The Government is attempting to sell up to 49 per cent of Mighty River Power, hoping to raise up to $2 billion from the stake. It is the first in a series of partial sales of state-owned companies that the Government hopes will raise $5b-$7b.

Labour leader David Shearer has said incentive for pre-registration will only benefit those who can afford to invest more than $2000.

Green Party co-leader Russel Norman said the Government was hoping to maximise the number of pre-registrations for political purposes, in an attempt to make the sales appear popular.

Those who pre-register are not making a commitment to buy shares, so it is uncertain exactly how much of the interest will translate into actual money.

- © Fairfax NZ News