Inclusive ep double differential cross sections for neutral current deep inelastic scattering are measured with the H1 detector at HERA. The data were taken with a lepton beam energy of 27.6 GeV and two proton beam energies of E-p = 460 and 575 GeV corresponding to centre-of-mass energies of 225 and 252 GeV, respectively.
The measurements cover the region of 6.5 x 10(-4) {= x {= 0.65 for 35 {= Q(2) {= 800 GeV2 up to y = 0.85. The measurements are used together with previously published H1 data at E-p = 920 GeV and lower Q(2) data at E-p = 460, 575 and 920 GeV to extract the longitudinal proton structure function FL in the region 1.5 {= Q(2) {= 800 GeV2.