A new silicon photonic integrated sensor based on the Vernier effect is proposed. Double performance can be achieved compared to state-of-the-art Vernier sensors. Half the operating bandwidth of state-of-the-art Vernier sensors can be employed. A rigorous and detailed modelling of the new Vernier devices is presented. <30000 ppm of NH3 in water and less than 5000 ppm of CO2 in air can be detected.