Greater Manchester Mayor Andy Burnham has said the region would consider a legal challenge if the Government placed it under Tier 3 coronavirus restrictions.
Government health officials are understood to be having discussions on whether to place the region in the very high category, making it subject to measures including the closure of bars, gyms and betting shops.
Speaking at an online press conference on Wednesday, Mr Burnham said if the region is placed into Tier 3 it would be "by imposition, not consent".
He said: "We are law abiding people, we would respect the law of the land.
"But we would consider other routes, legal routes, where we could protect our many thousands of residents who are going to be left in severe hardship in the run up to Christmas.
"We would not just leave them in the lurch, we would try and support them and that would include any legal action we could take on their behalf."
He said he thought a national circuit-breaker lockdown would be a "better and fairer way" of tackling the pandemic.
The Labour mayor said accepting a Tier 3 proposal without a financial package which included an 80% furlough scheme would be to "commit an act of self-harm", and would level down the region's economy.
He said: "We oppose the Tier 3 proposal and we will not cave in to all of the pressure that's being applied to us unless we can be given clear evidence, but more than that, the substantial financial support that's needed to protect our communities through this.
"We will not let them be levelled down by this Government through this pandemic.
"When I say substantial support, I'm talking about an 80% furlough guarantee across all of the sectors that would be required to close."
In a joint statement released earlier on Wednesday, Mr Burnham and the leaders of the 10 local authorities in the region insisted the area should remain in Tier 2 as the rate of infection and the hospital admission rate are lower than in the Liverpool City Region, which has been placed in Tier 3.