Clive Matthew-Wilson, publisher of online car buyers guide dogandlemon.com, said he hoped the Government would select more modest vehicles this time around.
"The things that concern me and I think many New Zealanders is the fact that most ministers are not meeting foreign dignitaries when they drive these vehicles.
"They are in fact doing relatively ordinary ministerial duties in cars that suggest that politicians get one deal and ordinary people get another.
"If the politicians could show some humility for a change they would buy basic vehicles like, say, Toyota Camry hybrids for the majority of their duties and buy a couple of luxury limousines merely for the job of picking up important people from the airport.
"Any one of the larger Lexus, Mercedes or BMW range would be the obvious contenders."
Green Party transport spokeswoman Julie Anne Genter said the National Government had the opportunity to show leadership by choosing low-emission electric cars.
"The performance of some electric car models, like the Tesla Model S, exceed the specifications needed for the Government's luxury limousines.
"They are cleaner, safer, quieter and cheaper to run and they may be cheaper. The list price of the current BMW limousines, purchased in 2011, is higher than the list price of the equivalent electric car."
The process of selecting replacement vehicles is expected to take six months and new cars will be progressively rolled out in the second half of 2015.
A spokeswoman for Mr Key said the budget for replacing the vehicles was confidential, "but the tender process ensures the Government is getting the best value for money".
She said the fleet was overdue for replacement.
"The cars are generally replaced every three years but we've kept the current fleet an extra year because they have continued to provide good service. The cars are being replaced now to ensure the fleet remains reliable and continues to provide the same level of quality of service."
Luxury v frugal
BMW 7 series: Standard diesel version 730 sedan has a 6-cylinder 3 litre engine, costs more than $193,700.
Mercedes S-Class: Mercedes premium sedan range starts from $206,890 for long-wheelbase versions.
Lexus: LS Hybrid: "The world's first prestige luxury V8 hybrid." Prices start from $262,000.
Toyota Camry Hybrid: "Class-leading fuel efficiency and smart features that can take you from sales trip to road trip in the blink of an eye" from $50,990.
Tesla Model S: Rechargeable electric car with a "spacious and luxurious interior". Has a range of at least 320km. Models start with the 302hp 60kWh base model at $90,000.