Public transport groups and some passengers have expressed anger after the price of new flexible season tickets was revealed.
The tickets, which went on sale on Monday, allow travel in England on any eight days in a 28-day period.
The Department for Transport (DfT) said part-time commuters on some routes will save hundreds of pounds a year through the scheme.
But larger savings can be made if some journeys are made at off-peak times, or using railcards.
Former transport minister Norman Baker, an adviser at Campaign for Better Transport, said the new tickets “do not appear to offer the kind of savings we had hoped for and are not comparable to the discounts for people commuting full-time”.
He added: “There appears to be no standard level of discount, and in some cases the flexible season ticket could end up being more expensive than the day return option.”
A number of passengers said they will end up paying more if they switch to the new tickets.
Trudie Thompson, 59, from Dover, Kent, claimed the tickets “will help very few people” and “will not encourage people to go back to commuting”.
She told the PA news agency that she plans to return to the office two days a week from September, but that using weekly season tickets will be £190 cheaper per month than the new Flexi Season ticket.
“The Government and rail companies are seriously misguided if they think the general public will be clamouring for this deal,” Ms Thompson claimed.
Graeme Douglas, who commutes from Faversham, Kent, into London, said passengers were “led to believe that the savings would be more substantial”.
“It was pitched as a game-changer,” he said. “We’ve been waiting months for the unveiling of this and it’s nothing more than a tiny shaving off the daily price if you commit to eight days over a month.
“It won’t save me any money. It’s better to try and travel off-peak and use a Network Rail card where possible. There’s zero real incentive here.”
But Kim Warren, 33, said she will save “around £500 a year” for her commute from Guildford, Surrey to the capital.
It will be “complicated to evaluate the cheapest travel options or when you need to renew”, she added.
According to an online season ticket price calculator, a passenger commuting three days a week from Cambridge to London King’s Cross via any permitted route will pay £5,745.60 if they use the new tickets.
That is more expensive than an annual ticket (£5,388), but cheaper than using weeklies (£6,999.01) or monthlies (£6,207.60).
For a two-days-a-week commuter, the new flexible tickets are the cheapest option over a year.
Commuters travelling three days per week from York to Leeds will pay £2,419.20 using Flexi Season tickets, compared with £2,516 for an annual ticket.
Monthly tickets would cost £2,899.20 over a year.
The scheme is the first step in major reforms of the railways announced last month in the Williams-Shapps Plan for Rail.
The paperless flexible tickets can be used from June 28.
A DfT spokesman said: “Flexible season tickets will offer most two and three-day-per-week commuters savings against buying daily tickets or traditional seasons.
“We have always been clear that passengers should consider which product best suits their journey and travel pattern. This will be easier than ever with the updated season ticket calculator.”
Manuel Cortes, leader of the Transport Salaried Staffs’ Association, said: “In some instances these are more expensive than Anytime tickets, which is simply short-changing passengers.
“Despite all the spin, people will not be fooled and nor should they be, because we want our railways to flourish as we recover from the pandemic.
“Transport Secretary Grant Shapps must go back to the drawing board and offer proper flexible season tickets which are good value for money, thus encouraging more people to use our railways.”
The introduction of flexible tickets comes amid changing travel patterns due to the coronavirus pandemic.
An increase in home working has led to a huge decline in the number of people travelling by rail, particularly those commuting rail five days a week.
Tickets offering discounts for part-time commuters were already available in Scotland and Wales.