The McLaren pair of Jenson Button and Fernando Alonso have been given a combined 55-place grid penalty for Sunday's Belgian Grand Prix.

Button and Alonso will start from the back of grid after McLaren changed the engines and associated elements in each of their cars.

McLaren's engine supplier Honda had already confirmed that Button and Alonso would be using their seventh engines of the season following the introduction of an upgraded power unit.

A new turbocharger, MGU-H and MGU-K have been put in both Button and Alonso's cars, with the latter has also used a new Control Electronics component.

Those changes have resulted in 25-place penalty for Button and a 30-place drop for Alonso.

As there are no longer in-race penalties for engine changes, McLaren are anticipated to use an eighth engine of the campaign in each car this weekend and incur further punishments.

That change will enable Honda to analyse data from the new power unit and give McLaren two new upgraded systems to use for the rest of the season without the risk of more sanctions.