The cross sections for neutral current deep inelastic scattering have been measured in e^-p and e⁺p collisions at a centre-of-mass energy of 318 GeV with the ZEUS detector at HERA using an integrated luminosity of 16 pb^-1 and 63 pb^-1, respectively. Single and double differential cross sections at high Q² are presented and compared to the predictions of the Standard Model. The structure function xF₃ has been extracted by combining the e^-p data with the recent ZEUS measurement of e⁺p neutral current Deep Inelastic Scattering (DIS) at a centre-of-mass energy of 300 GeV. The measured xF₃ is well described by the Standard Model using recent proton parton density functions.

PACS numbers: 12.15.--y, 14.20.--c