We report here a newly developed method for measurement of Li isotopes by use of multi‐collector ICP‐MS (Neptune) allowing rapid and high precision determination of Li isotope ratios at low levels of lithium (15–20 ng). The lithium reference sample solution IRMM‐016 was analysed over a period of ten months with an external reproducibility of 0.24% (2s, n = 52). Chemical separation of Li from matrix was performed on the seawater sample IRMM BCR‐403, for which a mean δ7Li value of + 31.0 ± 0.1 % (2s/√n, n = 31) was obtained. This mean value is in good agreement with those previously published for other seawater samples. BCR‐403 seawater being readily available, we propose that this seawater sample be used as a reference sample for Li isotope measurements.