Many media channels are covering the "fuel protests". According to BBC, the main reason behind these protests is fuel (especially diesel) prices raising:
The price of diesel, the most commonly used fuel in French cars, has risen by around 23% over the past 12 months to an average of €1.51 (£1.32; $1.71) per litre, its highest point since the early 2000s.
World oil prices did rise before falling back again but the Macron government raised its hydrocarbon tax this year by 7.6 cents per litre on diesel and 3.9 cents on petrol, as part of a campaign for cleaner cars and fuel.
The decision to impose a further increase of 6.5 cents on diesel and 2.9 cents on petrol on 1 January 2019 was seen as the final straw.
According to fuel-prices-eu, France already has a relatively high price for diesel fuel among European countries.
While the environmental justification makes sense, I am wondering about the urgency (a high price raise / time interval). Why not have a more smoothly increase?
Question: What are the reasons presented by the French government to explain why the price of diesel fuel increased so much in France?