Campaigners have applied for a judicial review into the government's handling of the Southern rail crisis.
Govia Thameslink (GTR) took over the Southern rail franchise in 2015 and its contract with the Department for Transport (DfT) runs until 2021.
Southern has been locked in industrial disputes with its staff.
The Transport for All campaign group said the government should have done more to ease disruption. The DfT said it could not comment.
A DfT spokesman said it was unable to do so while legal proceedings were ongoing.
Non-profit group Transport for All, which campaigns for travellers with disabilities and older travellers, has joined the Association of British Commuters (ABC) in requesting a judicial review into the DfT's handling of the Southern disputes, particularly in respect of the impact on older travellers and travellers with disabilities.
ABC applied for the review in January and is awaiting a decision from the Royal Court of Justice about whether it may proceed.
'Stuck on train'
A spokesman for the campaigners said: "Accessible public transport is a lifeline to inclusion for many disabled people who disproportionally rely on it to go about their everyday lives.
"The Southern rail crisis caused disruption and misery to disabled and older people, leaving many unable to travel to work and increasingly isolated. Yet throughout the strikes the DfT has remained silent."
Christopher Stapleton commutes from Balham in south London to Victoria in his wheelchair.
He said: "On roughly two-thirds of my journeys, when I arrive at Victoria there is no one there to assist me with a ramp, even though the staff at my home station have phoned ahead to let Southern Rail staff at Victoria know.
"So I end up stuck on the train.
"The effect of Southern's unreliable assistance is that every train journey becomes horribly stressful, and every time I arrive at my destination I have a tight knot of anxiety in my stomach - will there be someone with a ramp to assist me?"
A spokesman for Southern said: "We aim to give excellent assistance and are very sorry to hear about these passenger experiences.
"Over 440,000 journeys were made on Southern with disability railcards last year and only a tiny fraction resulted in a complaint that assistance was not provided.
"We regularly carry out call-back surveys with disabled passengers and 'mystery shop' so that we can look at what we can change to improve."