A group of North East MPs has written to Transport Secretary Chris Grayling demanding an urgent meeting about investment in the Metro.
Sunderland Central's Julie Elliott, Washington and Sunderland West MP Sharon Hodgson, South Shields' Emma Lewell-Buck and Jarrow's Stephen Hepburn are among ten signatories to a letter calling for action.
"The need to act is urgent," it says.
"Our constituents tell us that the poor reliability of the life-expired Metro trains is causing problems for them on a daily basis and we trust that, like us, you want to see the system preserved and expanded to new areas rather than crumbling away.
"We believe that investment is not optional and cannot be deferred. Nexus needs to go to the market this year if it is to have any chance of introducing new Metro trains in 2021 and it can only do so if the Government is prepared to stand behind it financially.
"If the new trains arrive any later, major timetable reductions are inevitable. The old stock is already failing.
"The Tyne and Wear public sadly know, from their daily experience, that Metro is failing due to mechanical obsolescence, with the failing rolling stock becoming a regular feature on the regional news outlets. They are also becoming acutely aware that the North East in general is a poor relation when it comes to transport infrastructure investment.
"In light of this, we were disappointed by the vague and non-committal response of Ministers to out questions on this subject in the House last week. This is not a new request.
"The need for public funding for replacement rolling stock as well as operating the system and infrastructure renewal has been discussed with the Government over many years and your department received the business case from Nexus a full year ago.
"We, therefore, request an urgent meeting with you to discuss the Metro and the steps you plan to make to assist Nexus.
"The Metro's importance to residents, businesses and general daily life in our constituencies is too great to be put to one side."
Emma Lewell-Buck said: "I have consistently raised concerns with relevant departments regarding the Metro since I was first elected in 2013, so I am delighted that so many of my Parliamentary colleagues have now come together to reinforce the urgency of this matter.
"Efficiency of the Metro is key to maintaining economic health in our area , so I was delighted when my campaigning paid off earlier this year and the Metro eventually came back into public hands after a succession of operational problems.
"However, what we now urgently need is for the DfT to release the funding for the new Metro cars, they have been sitting on the business case for one year now. That is yet another year that people across Tyne and Wear have had to endure avoidable and unacceptable delays.
"I will continue to press for swift action, as we all need a reliable, modern system."
Sharon Hodgson said: "Countless daily reports in the regional news show just how crucial it is for the Government to stump up the funding to upgrade the much dilapidated Metro network in Tyne and Wear, not only to ensure a smooth and stress-free journey for commuters but also for future extension of the line to Washington – as I have campaigned on for many years now.
"The Government must meet with myself and my regional colleagues to discuss this matter further; as it is becoming a matter of urgency."
Julie Elliott added: "The regular disruption Metro users are suffering while going to work or travelling around the region highlights just how badly investment is needed, particularly in replacing the near 40-year-old fleet of trains.
"As reported earlier this month, Sunderland will receive upwards of £1.3 billion investment in the coming years to regenerate our city. To fully benefit from this investment and for Sunderland to fulfil its potential it is critical that our public transport, including the Metro system, is fit for purpose.
"n 2016, six times more was spent on transport in London per head of population compared with the North East. This cannot be allowed to continue. The needs of Metro users in Sunderland and the wider region must not be ignored by the Tory Government any longer."
A Nexus spokesman said: "Nexus has been working for several years to secure funding for a new train fleet. The current fleet is almost 40 years old and its reliability is an increasing problem, causing trains to fail in service too often.
"A new fleet for the decades ahead will require external funding because of the significant cost involved, around £400million. We submitted a detailed business case to the Department for Transport last year and have been in talks with civil servants since; while there is agreement that Metro needs investment for new trains we are yet to agree a funding model."