At a meeting of the environmental scrutiny committee, councillors raised concerns about the emissions of the vehicles.
Cllr Caro Wild said: ‘Obviously we would have really liked to have made those electric vehicles.’
He said it was not possible to purchase an electric fleet because of limited grid capacity and the cost and availability of electric vehicles.
The new diesel vehicles will cost an estimated £9.7m.
Cllr Bethan Proctor said: ‘It did just feel a little bit disappointing that we are purchasing diesel vehicles two years after declaring a climate emergency.’
The council said that it would purchase some vehicles and lease others so that it could replace diesel vehicles with electric ones ‘when possible’.
It said it was looking at a solution to limited grid capacity at one of its recycling centres, Lamby Way, including a solar and wind project.
The proposed procurement will be considered by the council’s cabinet on 13 July. Cllr Wild said the cabinet ‘certainly had their eye on’ the ‘emissions of the vehicles’.