The new versions of BMW’s performance flagship SUVs, the X5 M and X6 M, have been unveiled.

Both are said to offer performance improvements of up to 10% over the outgoing models, while efficiency is said to receive a boost of up to 20%.

Both the X5 M and X6 M are powered by a 4.4-litre twin-turbo V8 that develops 575hp and 750Nm of torque.

Power is marshalled by a new eight-speed M Steptronic automatic transmission.

The performance figures for the X5 and X6 are identical, with both completing the 0-62mph sprint in 4.2 seconds, while top speed is electronically limited to 155mph.

Both record a combined cycle economy figure of 25.4mpg, while CO2 emissions of 258 g/km place them in the highest VED Band, M.

Keeping these two leviathans on the road is a revised suspension set-up that includes new upper front wishbones and more rigid bearings.

In comparison to standard X5 and X6 models, the M models feature firmer settings and a 10mm reduction in ride height, plus BMW’s Dynamic Drive active roll stabilisation and self-levelling air suspension at the rear.  Three settings – Comfort, Sport and Sport+ – allow the driver to personalise these settings according to mood.

Also uprated are the brakes, with six-piston fixed callipers at the front and single-piston floating callipers at the rear, both painted in dark blue.

The four-wheel-drive system has been revised, with changes to the Dynamic Stability Control system to provide Brake Standby, Brake Drying, Fading Compensation and Start-Off Assistant functions, while M Dynamic Mode allows a degree of drift before the safety systems activate.

Standard equipment includes metallic paint, Adaptive M suspension, cruise control, electric heated front seats, dual-zone climate control, infotainment system with 20GB hard drive and DAB digital radio, satellite navigation, and head-up display.

The BMW X5 M and X6 M are expected to arrive in the UK in April 2015, priced from £90,170 and £93,070 respectively.