The Department for Transport (DfT) has told the Tyne and Wear Metro operator Nexus to plan for a return to normal passenger numbers from April.
But Newcastle Liberal Democrat councillor Greg Stone said the working assumptions was "dangerously unrealistic", amid a surge in coronavirus cases and another national lockdown.
Nexus submitted a recovery plan to the DfT this week, outlining plans for the future of the service. Talks between the operator and the government are "ongoing", it said.
The DfT said it had set "central assumptions" for recovery plans for light rail services that were "indicative only and intended to achieve a level of consistency across operators" plans.
At the height of the first lockdown in the Spring, passenger numbers fell to 95%. The service has so far recieved emergency funding totalling £30 million.
The DfT has committed to providing cash support until April. Nexus says passengers numbers will not exceed 50% until social distancing comes to an end.
Councillor Martin Gannon, Labour leader of Gateshead Council and chair of the North East Joint Transport Committee, said: "We know that the Government understands how important bus and Metro services are for the North East and we're keen to agree a long-term plan for funding these vital services."
It's clear that the impact of the pandemic is still being felt and it's going to take a long time for public transport to recover fully. Government needs to provide something that recognises this going forward.
Passengers numbers on the metro are at around 16% of their normal levels, higher than during the first lockdown.
Nexus bosses say they will seek further emergency funding to avoid a reduction in services and a loss of passenger revenue.
A spokesperson said: "The Government has provided us with four financial support packages. These total £33 million and latest tranche of funding, allocated in October, will support Metro services until the end of March this year.
"The first lockdown saw passenger numbers fall to 5%. In the current lockdown it has fallen to 16%.
"If there is a drop off back to the levels of March 2020 then we might need to seek further support. The funding we have had in the current financial year is intended to cover our net losses in full."
A Metro recovery plan has been submitted to the Department for Transport. If restrictions are not lifted by April then our estimates will need to change. The main thrust of the recovery plan is to seek the continuation of emergency funding because we need financial support in order to stimulate demand and attract customers back to Metro, rather than have to cut service provision.
Newcastle Liberal Democrat councillor Greg Stone said a "crunch is looming for Nexus' finances", urging local leaders to put together a plan to avoid major cuts to the service in 2022.
The DfT said requests for future coronavirus funding "will be assessed in due course."
"We have been providing emergency funding to support light rail systems including the Tyne & Wear Metro throughout the pandemic, and will continue to work with operators during this difficult time.
"This funding has ensured that light rail services have continued to run, enabling essential journeys such as those made by NHS staff and other key workers.
"Once current restrictions are lifted, these services will also play an important role in our economic recovery."