An independent review is to be held into the emergency response to the Manchester Arena attack, the new Greater Manchester deputy mayor said.
Baroness Beverley Hughes said the operations in the aftermath showed the strain of spending cuts put on police.
Ms Hughes praised the way the emergency services' response to the 22 May suicide bombing which killed 22 people.
But, it comes in the light of cuts of up to 2,000 officers in Greater Manchester, since 2010.
More than 240 emergency calls were made in the wake of the arena attack, with 60 ambulances and 400 police officers in attendance, figures show.
Ms Hughes, who was officially appointed to the position which will oversee police and crime on Monday, said: "I would like to say that I think the police, emergency services, hospitals... staff who poured in that night and stayed there for days on end... everybody did put absolutely everything they could into responding.
"But there will be things that could have been done better and that's why we need a review, an honest review."
But, she also echoed concern from Greater Manchester's Chief Constable that a loss of 2,000 officers in seven years had left staffing at the "low end of reasonable".
The former home office minister said along with the Mayor Andy Burnham would be pressing the new government for more resources.
"The Mayor and I think we've got down to a level now that is not sustainable," she said.
The former Labour MP for Stretford and Urmston praised the way Manchester reacted to the attack which cost 22 lives.
"I went down to Wythenshawe Hospital and they've had to put a room there for all the things members of public have brought in for people injured and their families and so-on," she said.
"And everybody just wanted to do something they could, to be of help and show solidarity. It's great."
London Mayor Sadiq Khan also said police need extra resources following Sunday's terror attack in the capital.