Exclusive electroproduction of ϕ mesons has been studied in e±p collisions at s=318 GeV with the ZEUS detector at HERA using an integrated luminosity of 65.1 pb−1. The γ∗p cross section is presented in the kinematic range 2 GeV2<Q2<70 GeV2, 35 GeV<W<145 GeV and |t|<0.6 GeV2. The cross sections as functions of Q2, W, t and helicity angle θh are compared to cross sections for other vector mesons. The ratios R of the cross sections for longitudinally and transversely polarized virtual photons are presented as functions of Q2 and W. The data are also compared to predictions from theoretical models.