Building on an analogy with ordinary scalar field theories, an ε-expansion for rank-3 tensorial group field theories with gauge invariance condition is introduced. This allows to continuously interpolate between the dimension four group SU(2) × U(1) and the dimension three SU(2). In the first situation, there is a unique marginal ϕ 4 coupling constant, but in contrast to ordinary scalar field theory this model is asymptotically free. In the SU(2) case, the presence of two marginally relevant ϕ 6 coupling constants and one ϕ 4 super-renormalizable interaction spoils this interesting property. However, the existence of a non-trivial fixed point is established in dimension 4 − ε, hence suggesting that the SU(2) theory might be asymptotically safe. To pave the way to future non-perturbative calculations, the present perturbative results are discussed in the framework of the effective average action.