Hydrogen embrittlement, a complex phenomenon, hinges on interactions between hydrogen and the metal it permeates. It poses significant challenges across various structural materials, notably in ferritic steels. Hydrogen infiltrates steel, interacting with its atomic structure, resulting in micro-crack formation, subsequent propagation and eventual compromise of macro-mechanical properties. Hydrogen also plays a critical role in stress corrosion cracking, increasing the susceptibility to pitting. Lately, considerable advancements have been made in modelling hydrogen-assisted cracking by employing different computational techniques. The mode of fracture and crack initiation site were found to be influenced by the shear strength of the interface, highlighting the significance of accounting for mixed failure modes. This paper studies the effect of hydrogen on the failure stress of cracked plates subjected to mixed-mode fracture, wherein the coupled deformation-diffusion problem is solved using the phase-field method. The mixed-mode behaviour of crack growth is assessed for different levels of hydrogen concentration. A plate containing pre-existing defects in the form of corrosion pits is modelled for studying the crack propagation under uniaxial and biaxial loading conditions to predict hydrogen assisted failure in a corrosive environment. The study also investigates the influence of carbides and a dual phase microstructure on the hydrogen embrittlement.