An accurate inter-laboratory comparison (ILC) concerning the electrical quantities in low frequency between the laboratory for the calibration of multifunction electrical instruments of the National Institute of Metrology Research (INRIM) and a secondary high level electrical calibration laboratory was performed with satisfactory results. The instrument involved in the ILC was a top class multifunction electrical calibrator, chosen for its wide measurement fields and its excellent definability requiring therefore very small uncertainties to calibrate it. This ILC was the first high accuracy comparison exercise at INRIM involving a grid of about one hundred and thirty measurement points. The ILC allowed to check adequately the measurement capabilities, techniques and uncertainties of this secondary laboratory. Attention was paid to evaluate the correlated terms between the two laboratories measurements. The calibrator showed high stability and resulted more appropriate than fixed standards or than a 8.5 digits multimeter to the aim of the ILC.