Using an extension of the notion of polynomial time presentable structure we show that some natural presentations of the ordered field ℝalg of algebraic reals and of the field ℂalg of algebraic complex numbers are polynomial-time equivalent to each other and are polynomial time. We also establish upper complexity bounds for the problem of rational polynomial evaluation in ℂalg and for the problem of root-finding for polynomials in ℂalg[x] which improve the previously known bound.