The news means Oyster users could have to wait two years longer than those paying with contactless debit and credit cards before benefiting from the cap.
Transport for London is currently upgrading its fares system to allow holders of contactless debit and credit cards to pay for Train, DLR, Train and Tube fares at the cheaper Oyster rate.
The cards are already accepted on the bus network where they’ve been a big hit with passengers who have forgotten their Oyster cards or whose cards have insufficient credit for the journey.
Oyster card fares are subject to a daily cap but no cap is currently available to contactless card holders.
As part of TfL’s upgrade, both contactless and Oyster card users will benefit from daily and weekly caps meaning passengers who make enough qualifying journeys will pay no more than the cost of a weekly Travelcard.
The Mayor and TfL have previously pledged that Oyster users will always have access to the cheapest fares.
The Mayor’s letter repeats that commitment but states weekly capping for contactless cardholders will be introduced ahead of Oyster cardholders due to “greater flexibility” in the contactless system.
In his letter to Caroline Pidgeon, Mr Johnson says the work to introduce weekly capping “has to be delivered in phases” and that it would be wrong to delay introducing weekly capping for contactless cardholders until the caps were also available to Oyster users.
His letter says: “If existing Oyster pay as you go users would like access to weekly prices but do not want to use, or do not have access to, contactless payment cards, then they can continue to use their Oyster cards and buy a 7-day bus pass or Travelcard until we introduce weekly capping on Oyster pay as you go in 2015. The only difference here is that current Oyster users would need to make a decision in advance to purchase a weekly bus pass or Travelcard.
“The lowest Oyster price is thus currently available to all our customers and will remain so, including for those who do not want to, or cannot, use contactless payment.
“All of the above will be made very clear to customers in our communication with them.
“We could, of course, choose not to offer weekly capping to those using contactiess payment until we are able to introduce it on Oyster too. However, I do not think it is right to deprive users of contactless payment of this facility when the price for weekly travel is already available to all customers, including those who use Oyster.”
Speaking last year Assembly Member Pidgeon said Assembly Members wanted to ensure all passengers had access to the cheapest fares and would “keeping a close eye” on developments.