Lotto New Zealand's biggest ever jackpot must be won this Saturday, but the hype and allure of riches will hurt problem gamblers, advocates say.

The first division powerball prize has reached $50 million, sparking a flurry of ticket sales and endless conversations and dreams about what could be done with that much cash.

But the prize has also lead to concern, as the Problem Gambling Foundation knows the extra excitment will encourage people to spend more.

Pesio Ah-Honi, the director of Pacific Services at the Foundation, says that although Lotto is less harmful to the community than pokie machines or other online games, it does take money from families who can't afford it.

She predicts the $50 million jackpot will encourage people to gamble money they can't afford to lose.

"We do see an increase in spending with the jackpot increases, we see an almost addicition-like behaviour that people don't normally display," she says.

Ah-Honisays powerball is less addictive than other forms of gambling, as it delays gratification.

But in recent years, the Problem Gambling Foundation has seen an increase in people worried about their Lotto use, she says.

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Gambling harm experts are worried about the $50 million Lotto jackpot.

"When a jackpot is so high, it tends to get people thinking they need to buy more to be in to win. There's potential risk of people spending more than what they can afford," she says.

There's a $150 weekly limit for spending on the My Lotto website, with a $500 monthly limit.

ButAh-Honisays that is too much for some families. "For a lot of people,$150 a week on Lotto is $150 more than they can afford."

"We are always concerned that people who can not afford it will buy a ticket. Their families are going withoutbecauseof money being put on powerball this week."

Lotto offers services to help addicted gamblers, including a 'self-exclusion' form to ban yourself from Lotto stores.

On the site, users can block themselves from playing certain games.

In statements, Lotto encourages people to play only for fun. "This isallabout having fun, being informed and knowing your limits," it says.

University of Auckland professor of biostatistics Thomas Lumley said the chance of getting the winning numbers - all six Lotto numbers plus the Powerball - was 1 in 38 million per line.

GAMBLING ADDICTION HELP:Gambling Helpline - 0800 654 655 or text 8006.Problem Gambling Foundation - 0800 664 262 or help@pgfnz.org.nz

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'Families are going without': Problem gambling advocate's concern for $50 million Lotto jackpot - Stuff.co.nz