Around one in three trains are not meeting modern accessibility standards and even by 2019 a quarter of all rail journeys will still depart from stations that are not step-free.
Transport minister Paul Maynard has conceded that currently only 70% of train fleets operating passenger services are up to standard and passengers will have to wait for at least another two and half years before the problem can be solved.
DfT is considering expanding £20m new station fund
Mr Maynard told Parliament: 'We are committed to improving accessibility of the rail network. Currently 70% of train fleets operating passenger services meet modern accessibility standards, up from just 39% as at January 2011, with the remaining vehicles due to be either upgraded or replaced by 1 January 2020.
'We are continuing to improve station access through the Access for All programme and other major projects such as Thameslink or Crossrail. By 2019 at least 75% of all journeys will be from stations with step-free access.'
On the nation's busiest networks in London, mayor Sadiq Khan recently outlined plans to improve accessibility through his draft mayoral transport strategy.
The document highlights that currently '45% of disabled Londoners find travelling by public transport stressful'.
Among the long-term targets, the mayor plans to 'halve the additional journey time required by those using the step-free network only, so that journey times on the step-free network become comparable to those on the wider public transport network' by 2041.
There are also plans to upgrade 54 Tube stations to step-free by 2030 and to upgrade stations on the national network at a rate of five to 10 stations every five years under the Access for All programme.
One crucial issue for wheelchair users, highlighted by the recent 'Paulley Principle' ruling, is the competition for space on buses between wheelchair users and pushchairs.
The document states: 'The mayor, through TfL, will continue to provide improved accessibility training to all bus drivers, and will ensure that new buses provide better accessibility for all users, including more onboard space for wheelchair users, improved boarding ramps and induction loops.'
Catherine Smith, campaigns officer at Transport For All - a London mobility charity providing support to disabled and older passengers - said the plans were a positive step forward.
'We are happy with the broad targets and aims, which take long-term steps towards a more inclusive system. However we want to see more short-term targets and more detail on how this is going to be delivered. We would like to see short-term projections on Tube accessibility,' she told Transport Network.
'There is not enough about door-to-door services, given the ageing population and how many people will come to rely on it. We would like to see a more holistic approach to step-free journey times looking at the network as a whole.
'There is a really positive commitment to improve bus designs to make them more inclusive. We would really like to see them introduce buses with separate wheelchair and buggy spaces.'
Ms Smith also called on the mayor to exert influence on regional rail services such as the South Eastern franchise, which is currently being relet, to demand turn-up-and-go services for disabled passengers rather than forcing them to book in advance for assistance.