By Ilaria Grasso Macola The RAC has called on Big Four supermarkets such as Tesco to further cut fuel prices as diesel and petrol prices fell by around 9 per cent in December. Data published today by the motoring group show that petrol went down by 8.4p to 151.1p per litre in December, whilst diesel decreased by 9.4p to 173.9p per litre. This brought down the price of filling up a 55-litre family car by £4.63 and £5.19, for petrol and diesel respectively. Nevertheless, the RAC has called on supermarkets to slash fuel costs by a further 11p, as the wholesale price of petrol and diesel has remai…