From October of this year, the game will feature an additional 10 balls, with players having to select six balls from a total of 59.
Camelot said Lotto will also offer larger rolling jackpots, with average jackpots expected to triple the level of current winning amounts.
A new ‘Millionaire Raffle’ game will accompany the main Lotto draw on Saturdays and Wednesdays, guaranteeing at least two winners of £1 million (€1.4 million/$1.6 million) each week.
Camelot said that the chance of winning at least £1 million on the new game will be better than winning the jackpot under the current Lotto format, with odds at one in just under 10 million, compared to one in just under 14 million at present.
In addition, players will now win a free Lucky Dip ticket for a future Lotto draw by matching just two numbers on the main draw.
Camelot said the Match 2 prizes will create an additional 1.8 million winners each week, thus increasing the overall chance of winning any prizes from one in 54 on the current game to one in 9.3 from October.
Andy Duncan, chief executive of Camelot UK Lotteries, 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 program of continuous innovation and builds on Lotto’s ongoing success.
“New ideas and fresh, enticing prizes will keep the game healthy and thriving – ultimately delivering even more for players and Good Causes.”