BARCELONA - Formula One championship leader Max Verstappen led Sergio Perez by a huge margin in a Red Bull one-two in first practice for the Spanish Grand Prix at Barcelona's Circuit de Catalunya on Friday.

The Dutch 25-year-old's best lap of one minute and 14.606 seconds on soft tyres at a circuit that has gone back to the layout last used in 2006, was 0.768 quicker than Mexican Perez.

Verstappen, who took his first F1 win at the circuit in 2016 and also won last year, leads closest rival Perez by 39 points after winning four of six races.

Red Bull have won all six so far.

Alpine's Esteban Ocon, fresh from third place in Monaco last Sunday, was best of the rest despite shedding some rear bodywork in the hour-long session on a hot afternoon but 0.812 off the pace.

Nyck de Vries was a surprise fourth for Red Bull-owned AlphaTauri ahead of Alpine's Pierre Gasly and home hero Fernando Alonso in the Aston Martin.

Ferrari introduced a new look upgraded car but Charles Leclerc and Carlos Sainz were eighth and ninth with Mercedes' George Russell, who had been trying out prototype Pirelli tyres for much of the session, 10th.

Leclerc ran the old design and Sainz the new bodywork as Ferrari conducted a comparison.

The top teams were all running with sensors and fluorescent 'flow-vis' paint early in the session as they sought aerodynamic data.

Several drivers also complained about the bumpy approach to the final corner.

(Reporting by Alan Baldwin, editing by Christian Radnedge)