It has been a year since Northern Ireland's 26 councils were reduced to 11 - with the new bodies given wider responsibilities.
Fiona McCandless told the BBC's Inside Business programme the Planning Service was pleased with the transition.
"The councils were sufficiently resourced to deal with the applications transferred to them," she said.
"They had the necessary skills and resources to deal with that.
"Time have proven that the backlog cases that the department previously dealt with have been really significantly reduced.
"The councils now are dealing with the cases that have been submitted, more since 1 April last year."
You can hear more on Inside Business on Radio Ulster at 13:30 BST on Sunday.

Det Con Chris Maitland, 40, faces 14 charges, including sexual touching of a girl aged under 13 and making indecent images of a child.
The officer appeared at Westminster Magistrates' Court earlier and was remanded in custody.
He is next due to appear at Southwark Crown Court on 15 April.
Det Con Maitland, who works in the force's Sexual Offences, Exploitation and Child Abuse Command, was originally arrested in November on suspicion of possession and distribution of indecent images of children.
He was arrested again on Tuesday on suspicion of sexual touching of a young girl in Waltham Cross, Hertfordshire, in October 2005.
It is alleged the officer, of no fixed address, possessed 818 images and videos, ranging from the most serious category A to the lowest category C.
He also faces five counts of taking an indecent image of a child and seven of making an indecent image of a child.
Mr Maitland is currently suspended from duty.

Hendry, who retired in 2012, has seven Crucible titles to his name, while O'Sullivan has won snooker's showpiece event on five occasions.
"Ronnie is the best player to ever pick up a cue," Bingham, 39, told BBC Sport.
"But to be the greatest player you have to beat the records."
O'Sullivan, 40, is looking to go within one world title of the Scot, who won a total of 36 ranking titles, when this year's event gets under way on Saturday.
Bingham added: "Hendry was a born winner; he only loved winning and he was more ruthless than anyone. Ronnie is the most talented and the best in the world, but to be the greatest ever you need titles."
Bingham beat O'Sullivan on his way to lifting snooker's biggest prize in Sheffield for the first time last year and he is in no doubt that the unpredictable talents of the 28-time ranking event winner make him the man to beat once again.
"He is the only person in the game who has the aura that Stephen Hendry and Steve Davis had," Bingham added.
"Whatever tournament he enters, he is probably going to be favourite - and rightly so. He is the best player in the world."
Bingham said the game's best players were capable of toppling O'Sullivan, but it was also a matter of believing it, and lasting the distance at the 17-day tournament.
"Anyone now in the top 16 will fancy their chances," the Basildon-born potter said. "But, when it comes down to the crunch, to actually beat Ronnie, it's a different ball game.
"I remember saying to Ronnie last year: 'How have you won it five times?' I won it last year and it took me three weeks to get over it.
"How he has done it five times I will never know. It just shows you what a class act he is."
The chief planning officer has said the transfer of planning powers to the new super councils has been a success.
[NEXT_CONCEPT]
A Met Police detective working in a child abuse investigation unit has appeared in court accused of a string of child sex offences.
[NEXT_CONCEPT]
Ronnie O'Sullivan must match Stephen Hendry's World Championship title haul to be considered snooker's greatest player, according to reigning world champion Stuart Bingham.