Train tickets from Brighton to London will rise by as much as 10.8% in January.
A Brighton to London season ticket on Southern rises 7.76% in January, going up from £3,556 to £3,832, while an Eastbourne to London season ticket increases 7.77% to £3,940.
Some off-peak Brighton to London day returns will rise 10.18% to £24.90 in January.
A weekly First Capital Connect season ticket from Brighton to London will rise from £77.60 to £80, and an annual ticket from £3,104 to £3,200 (3.1%).
A spokesman said: "First Capital Connect will continue to offer the cheapest prices for travel in and and out of London."
The Association of Train Operating Companies (Atoc) says nationally, fares will rise by an average of 6.2%.
Campaign for Better Transport's public transport campaigner Alexandra Woodsworth said: "These astronomical fare rises make a mockery of the Government's commitment to fair pricing for rail travel.
"Season tickets will cost hundreds of pounds more in the new year, and thousands of pounds more by the time of the next election.”
Gerry Doherty, leader of the TSSA rail union, said the rise was "simply outrageous".
Under the current annual price cap formula, fares can only increase each January by the previous July's RPI inflation rate plus 1%.
This means that in January 2011, regulated fares will rise by an average of 5.8%.
But this year, the Government has reintroduced the flexibility rule, which gives operators a 5% leeway on this, as long as overall the average rise nationally adheres to the cap.
And further misery will await passengers in January 2012 when the annual price rise formula changes to RPI plus 3% across the network.
Atoc chief executive Michael Roberts said today: "We know times are tough for many people but next year's fare increases will ensure that Britain can continue investing in its railways.”
He added that taxpayers still contributed to half the cost of running the railways.
Earlier this week, an objection from First Capital Connect led to the rail regulator scrapping plans for better Southern services between London and Brighton.