The National Lottery is introducing more numbers and bigger jackpots in sweeping changes to the game later this year, but statisticians say scooping the big prize is more elusive than ever.
Lotto players will have to select their winning numbers from a pool of 59 - up from 49 - from October.
National Lottery operator Camelot claimed the "enhancements" will actually give players a better chance of winning and better odds of becoming a millionaire.
But statisticians point out that the chance of matching all six balls will decrease from one in 14 million currently to one in 45 million.
Camelot said a new Millionaire Raffle will guarantee at least one millionaire per draw, the average winning jackpot is expected to be triple the current level, and the chances of winning at least £1 million will be better than the chances of winning the jackpot on the current game, with odds at one in just under 10 million compared with one in just under 14 million on today's game.
Players who match two numbers will win a Lucky Dip ticket for a future draw, which Camelot said would create an extra 1.8 million winners a week and increase the overall chance of winning any prize from one in 54 currently to one in 9.3.
The cost of playing will remain at £2 a line, and other prizes such as £25 for matching three numbers will also stay the same.
Statistican Robert Mastrodomenico said: "Whilst it may be the case that the new Millionaire Raffle will increase your chance to become a millionaire, moving from 49 to 59 balls makes it more unlikely to win the jackpot if we need to match all six balls."
He calculated that the chance of matching all six numbers from 59 balls would increase to precisely one in 45,057,474.
"So whilst the spin is that we will see more millionaires, the reality is that the chance of you winning the big one has become less likely," Mr Mastrodomenico said.
Dr John Haigh, emeritus reader in mathematics at the University of Sussex, said: "I will continue not to buy tickets, but that's just me.
"The chance of winning the jackpot, which at the moment is one in 14 million, will be one in 45 million when the extra 10 balls are added.
"But because the chance of winning the jackpot is lower, when you do win the amount will be higher.
"This will also mean a lot more rollovers, and they create excitement. I expect Camelot will see this as an exciting feature."
Camelot chief executive Andy Duncan said: "Lotto has enjoyed two years of consecutive growth since we re-invigorated the game in 2013 and has already delivered over £250 million more to Good Causes than if we had done nothing to change the game.
"What we're announcing today - offering players more chances than ever to become a millionaire on Lotto and bigger rolling jackpots - is part of our programme of continuous innovation and builds on Lotto's ongoing success."
Camelot is yet to reveal the exact October launch date.