§ 25. Increasing compensation during fiscal year prohibited. The board of estimate and apportionment of any city or the body exercising similar functions in any city, excepting a city of the first class having a population of more than five hundred thousand and less than one million, is hereby prohibited from increasing the compensation of any office or position, except compensation on per diem basis, paid out of the treasury of such city, during any fiscal year, after the same shall have been fixed and provided for in the budget of such city for such fiscal year.