The entire Ford range is affected, with prices going up by an average of 4.7%.
List prices for entry-level cars are now:
Vauxhall is increasing prices on all models, apart from the Vectra and VXR8, by an average of just under 5%.
Haggle hard, though
While list prices are rising, buyers are reminded that there has never been a better time to buy a new car, and that they should haggle as hard as ever for discounts.
Both companies say the price rises are necessary because of sterling's weak position compared with the Euro.
As a result, they have also warned that future currency fluctuations could lead to further price rises.