Labour has pledged to renationalise most railways saying the current model is 'broken'.
The party says it will meet the pledge by bringing passenger services into public control as the contracts for current franchises expire.
Shadow transport secretary Louise Haigh said there would still be a role for the private sector under the plans.
However, rail minister Huw Merriman said the plans were "pointless" and "unfunded".
Louise Haigh has said Labour will renationalise the network
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Haigh, the MP for Sheffield Heeley, told Sky News: "We know the current model is broken. Anyone who has had to rely on the railways recently knows that very well. We have got record delays, record cancellations and routine overcrowding. That is because the system just isn’t set up in a way that works for the passenger.
"So, for too long we have had this really fragmented model that means dozens of operators and interests work against each other rather than work in the interests of the passenger."
Haigh pointed to the example of delays, which she claimed led to "armies of lawyers" arguing with each other "about whose fault it is and who has to pay for the mistake rather than work out how to fix it."
She added: "That is why we want to sweep away that model and bring in a unified, simplified, publicly owned railways that can from top to bottom work in the interest of the passenger."
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Labour said they were not planning to nationalise rail freight companies or rolling stock companies
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However, there has been some concern from Conservative ministers, who raised questions about the funding for the plans.
Defence minister and MP for South Suffolk James Cartlidge told Sky News: "Privatisation led to a doubling of the number of people using our railways. It has been a significant success story, huge investment from the private sector.
"But as I said, if that investment hadn’t come from the private sector it has to come from somewhere, and it would have to come ultimately from taxpayers.
"I think that is the key question for about this policy: How much is it going to cost taxpayers? At the moment it is unfunded."
Lumo operates trains on the East Coast Main Line between London King's Cross and Edinburgh Waverley
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Under the plans, Labour would still allow privately financed "Open Access operators", such as Hull Trains and Lumo, to continue. It is also not planning to nationalise rail freight companies or rolling stock companies.
Chief executive of Rail Partners Andy Bagnall said: "Train companies agree that change is needed for the railways, but nationalisation is a political rather than a practical solution".
"Since the pandemic, train companies have been effectively renationalised and subject to a level of micromanagement by government not even seen under British Rail."
Liberal Democrat transport spokesperson Wera Hobhouse said: "[The Conservatives] left commuters paying higher prices for poor services and endless disruption. The Liberal Democrats want a plan which puts commuters first by establishing the Great British Railway body after years of the government dithering."
