Such sums as may be prescribed by His Majesty in Council shall be charged on the revenues of the Federation in each year as grants in aid of the revenues of such Provinces as His Majesty may determine to be in need of assistance, and different sums may be prescribed for different Provinces:
Provided that, except in the case of the North West Frontier Province, no grant fixed under this section shall be increased by a subsequent Order, unless an address has been presented to the Governor-General by both Chambers of the Federal Legislature for submission to His Majesty praying that the increase may be made.