RAF Northolt is to shut for eight months next year while its runway is resurfaced and safety improvements are made.
The military airport is used frequently by the royal family, who will have to fly from a different base while £45million renovations are carried out.
Fixed-wing aircraft from No. 32 (The Royal) Squadron, which are currently based at RAF Northolt, will move to RAF Benson while the works take place, although rotary operations will continue from Northolt.
Shadow Communities Minister Gareth Thomas raised concerns that the changes are paving the way for more commercial flights at the airport.
Last year, there were 10,000 commercial flights, against 3,800 military ones.
Mr Thomas fears the number of commercial flights could increase to 50,000 a year, as proposed in a report in 2012.
At a Westminister Hall debate today, the MP for Harrow West called the military status of the airport a "smokescreen", saying:
"The simple fact of the matter is that Northolt is no longer in practical terms a military airport. The vast majority of flights are now commercial ones."
RAF Northolt’s classification as a military base means it does not have to comply with the rules of a civilian airport, including the need to get planning approval for changes to the runway and increasing the number of commercial flights.
Defence Minister Tobias Ellwood, responded to Mr Thomas, saying:
"It is used and needed by the military every single day, but it is true for a number of decades it has been under utilised in this role."
Mr Ellwood insisted there was "no current active planning" to "revisit the decision" to restrict civilian flights to 12,000 a year.
"When the runway reopens, nothing will change as to what exists today, the same stringent terms and conditions on civilian movements that have been in place for many years, and were reaffirmed in 2013, will remain in place."
He also clarified that the airport has the capacity to accept military contingency requirements which may displace commercial movements at any time for the national benefit.
An RAF spokesperson, meanwhile, said:
"Civilian flights at RAF Northolt will continue to utilise spare capacity to ensure we get the best return for the taxpayer."
"There are no plans to revisit the decision taken by Ministers in 2013 to set the cap in civil movements at 12,000.
"The closure of the airfield for renovation in 2018 is for military requirements and has no association with further commercialisation. Following reopening, the cap in movements will remain the same. Likewise scheduled airlines are not permitted at RAF Northolt."
In October last year, the then Flybe CEO, Saad Hammad, left the company after he called on the Ministry of Defence to allow the airline to use RAF Northolt.