The upgrade, which comes from engine tuner Mountune, costs £1195 and takes two hours to fit at a main Ford dealer. The upgrade includes a new large capacity intercooler and air filter, as well as remapped software. As well as increasing maximum power, the upgrade also improves torque from 254lb ft to 295lb ft at 2750rpm.
Ford hasn't revealed how the upgrade affects the car's 0-62mph sprint time or top speed - which currently stands at 6.5 seconds and 154mph respectively. The upgrade makes the Focus ST more evenly matched against key rivals like the 276bhp Seat Leon Cupra, the Vauxhall Astra VXR and the 296bhp Volkswagen Golf R.
Ford's UK sales director Kevin Griffin said the Mountune upgrade would allow Focus ST owners "to experience even more impressive performance, while offering the reassurance that the upgrade will not affect warranties."