Victoria's Public Lottery Licence has been amended so from May 11, the Oz Lotto matrix will increase from seven from 45 numbers to seven from 47.

Three supplementary numbers will be drawn instead of two, resulting in 10 numbers drawn from 47.

The changes, the first to the game since 2005, decrease the odds of winning first division from one in 45.3 million to one in 62.8 million, the Victorian government gazette says.

The move will affect Oz Lotto entrants in all states and territories since the game, played nationally every Tuesday, is licensed in Victoria.

The Lott spokesman Matt Hart said the changes were made in response to feedback from lottery players.

"Players told us they wanted Oz Lotto to offer the potential for more winners and bigger prizes, and that's exactly what we've given them," he said.

Under further changes, he said Oz Lotto's base jackpot will increase from $2 million to $3 million and punters will be offered extra prizes, increasing the chances of winning other divisions from one in 55 to one in 51.

Australia's peak body for lotteries and newsagents said the cost of each game would rise 10 cents, from $1.20 to $1.30, to accommodate the larger base jackpot and give struggling agents a boost.

"The small increase in price will assist retailers and their staff to weather this more challenging trading environment with rapidly rising costs," Australian Lottery and Newsagents Association chief executive Ben Kearney said.

Opposition gambling spokeswoman Steph Ryan accused the state government of a cash grab, suggesting the changes would lead to more tax revenue for Victoria.

"By adding extra numbers to the lottery, the government is ensuring that it's harder to win, which means it's going to jackpot more, and bigger jackpots lead to bigger ticket sales," she told reporters on Thursday.

While rates differ across states and territories, Victoria collects 79.4 per cent of losses from public lottery tickets sold in Australia and 90 per cent from those bought overseas.

Victoria's lottery revenue was $584 million in 2021/22, up from the $559 million the State Revenue Office collected in the previous financial year.

Before the first-division Oz Lotto odds decrease, the 2021/22 state budget forecast the figure would rise to $631 million by 2024/25.

Alliance for Gambling Reform chief advocate Tim Costello said the government was pursuing tax revenue over gambling harm reduction.

"There is absolutely nothing in this decision that reflects any approach to gambling harm reduction. It is simply driven by the Victorian government's desire to increase gambling tax revenue," he said.

Sport and Events Minister Martin Pakula dismissed concerns the game would be harder to win, saying the differences were "pretty academic".

Premier Daniel Andrews questioned the accuracy of opposition and advocate claims, but deferred to Gaming Minister Melissa Horne, who declined to comment when contacted by AAP.

It is understood the state government believes the amount of overall payout to players will not change, nor increase gambling-related harm.

A new two-licence model for Keno was also recently announced for Victoria, allowing incoming licensees Tabcorp and Lottoland to operate online from April 15.

Australian Associated Press