Chair of the Commons Defence Select Committee Tobias Ellwood has warned now is not the time to cut the UK's tank capabilities.
The comments follow reports that next month's Integrated Defence Review will recommend major cuts to personnel and resources.
According to The Times, officials are considering upgrading 150 Challenger 2 tanks to prepare them for the next generation of warfare while 77 could be scrapped.
The Challenger 2 is the British Army's main battle tank and although state-of-the-art, it has now completed 23 years' service.
Mr Ellwood voiced concerns when speaking to Forces News: "We actually don't know that fundamental question about what our Armed Forces are expected to do on the international stage and meeting new and emerging threats."
He added that reports of cuts have "taken everybody by surprise" because "we don't know where we might be utilising our land forces".
It is understood the Army's 758 Warrior infantry fighting vehicles could also be retired and replaced by 500 new armoured personnel carriers ahead of schedule.
Mr Ellwood said: "If you have 150 challenger tanks, they need to be supported, and they need to be supported by armoured fighting vehicles, that means something with a cannon on top, at least a 30 or 40mm. We don't have anything.
"If you take Warrior out of that – it's a bit like sending the Lancaster Bombers out without Spitfires or Hurricanes.
"The Boxer does not qualify, neither does the newer vehicle coming online, the Ajax.
"They’re both very good vehicles and I'm pleased to see the Boxer, which will be part of our strike brigades and help with stabilisation but, ultimately, if you're going to keep your main battle tank, it needs to be supported otherwise you may as well scrap it as well," he added.
In response to the latest speculation about the Integrated Review, the Army's Head of Strategy, Brigadier John Clark, said "how we compete and fight is changing all the time and the way of operating must change accordingly."
Major General (Ret’d) Tim Cross, a former commander of British personnel in Iraq and Kosovo also told Forces News he is worried the Army could be set to lose thousands of troops as a result of the Integrated Review.
He said he fears as many as 10,000 troops could go.
It has been billed by the Government as the deepest and most radical re-evaluation of the UK’s place in the world since the Cold War ended.