The diffeomorphism and Weyl transformations in the renormalized D-dimensional phi ⁴ theory are considered. The action functional including the sources of the operators phi ² and phi ⁴ appears to be invariant with respect to these transformations with the appropriate choice of their form for the field and sources. For the generalized diffeomorphism transformation being some combination of diffeomorphism and Weyl transformations, the Ward identities for the renormalized Green functions of the field phi and operators phi ², phi ⁴ are obtained. In the critical point they are similar to the Ward identities used in the 2D conformal field theory and enable one to prove the conformal invariance of phi ² and phi ⁴ for arbitrary dimension D.