About $200 million has been paid to transport consultants for work on five of the seven roads of national significance since 2009.
Information released to Radio New Zealand under the Official Information Act shows $216 million has been spent on investigation and design work on the Puhoi to Wellsford highway, Auckland's western ring, the Waikato expressway, Wellington's northern corridor and Christchurch motorways.
Of this, $200 million was paid to consultants, with $92 million for work on Wellington's northern corridor.
The New Zealand Transport Agency told Radio New Zealand that using professional consulting firms to plan, investigate and design road projects was standard practice, and it was not unusual for 10-15 percent of a project's cost to be spent on design work and planning.
The seven roads of national significance, which also include the Victoria Park Tunnel and Tauranga Eastern Link - are forecast to cost more than $10 billion over the next decade.
Labour transport spokesperson Phil Twyford told Radio New Zealand it was an "eye-watering amount of money" to be spending on consultants in the current economic climate.
"It really puts a big question mark over the roads of national significance and how much money is being ploughed into these gold-plated projects.
"$200m could buy a lot of useful transport infrastructure and services," Mr Twyford said.
Green Party transport spokesperson Julie Anne Genter questioned the impartiality of the advice given to NZTA by consultants.
"In does beg the question of whether the transport consultants' industry is actually giving advice that's totally neutral or whether they're recommending projects they know are going to result in more work for them," she told Radio New Zealand.