Rail firms have taken out a half-page newspaper advert to offer a "sincere apology" for their "ongoing problems" since the introduction of new timetables.
South-east England train operators Thameslink and Great Northern, in partnership with Government-owned Network Rail, wrote that the service "has not been good enough" after the rescheduling of all trains on May 20.
In the ad in Metro newspaper, the organisations acknowledged that "we failed to launch new services as planned", which has resulted in "significant delays, cancellations and disruption".
The letter stated: "We apologise sincerely and unreservedly for the impact this has had on your daily lives."
A third new train timetable in two months - which will be introduced on July 15 - will be "more dependable" and prioritise peak trains to give "more certainty to plan your journeys to and from work", the advert pledged.
An interim timetable was introduced on June 4 which saw around 6% of daily services removed, but reliability has continued to struggle.
On Sunday it was reported that Govia Thameslink Railway (GTR) - parent company of Thameslink and Great Northern - could be about to lose its contract.
The company was said to be "drinking in the last chance saloon", according to an unnamed Government source quoted by the BBC.
GTR chief operating officer Nick Brown has written to staff stating that "nothing has changed" and the company is "continuing to work within the terms of our contract".
The firm also issued a document giving employees a "clear summary of what has happened over the last two months", including an explanation of why postponing the introduction of the new timetable "was not an option".
The Rail, Maritime and Transport union accused GTR of "playing for time and treating passengers and staff like a bunch of mugs".
General secretary Mick Cash said: "GTR have taken the blame game to a whole new level in this barrage of propaganda which takes their passengers and staff for a bunch of mugs who can be fobbed off with any old garbage.
"It is unbelievable that they think they can get away with this patronising nonsense."
GTR chief executive Charles Horton resigned last month.
A series of failures have been blamed for causing the chaos, including Network Rail's late approval of the new timetables and delayed electrification projects, poor planning by train operators and the decision by transport ministers to phase in the introduction of new GTR services.
The damaging impact of the new train timetable was demonstrated in punctuality figures published by Network Rail on Monday.
More than a third (36%) of Thameslink trains were delayed by at least five minutes between May 27 and June 23, compared with 18% in the same period last year.
The proportion of Great Northern trains failing to hit the punctuality target rose from 16% to 30%.
Northern - a separate franchise operating in the north of England - saw almost a quarter (23%) of trains at least five minutes late, compared with just 9% during the corresponding period last year.