It was ranked at 14th by the Road Users' Alliance (RUA), based on the length of the network relative to the size of the gross domestic product.
'This is not how we foresaw the future when the Government announced its New Deal for Transport,' said Road Users' Alliance director Tim Green. 'Apart from the misery to motorists and communities desperate for bypasses, what does it say to manufacturers seeking to invest in just-in-time logistical efficiencies? The logic is to move abroad, which has negative implications for employment and tax revenue.'
The RUA says the UK's main competitors, such as France, Germany, Italy and Spain, all have motorway networks double or more the size of the UK's.
And it says that while UK road user taxes in the year 2001/02 added £44 billion to the Treasury's coffers, less than a quarter of this was spent on transport and only £5.8 billion on roads.
Green added: 'Investment in public transport may be desirable, but diverting the majority of transport spending to rail will not affect the demand for roads.
'Road travel accounts for 92% of all passenger travel and this picture is reflected in Europe, even in countries which have highly developed rail, bus and bicycle infrastructures.
'With the number of cars on the road set to increase dramatically, we simply cannot afford to ignore the need for improving our road system. It is time for the Government to drive forward plans for an improved road network if we are to remain a credible force in Europe.'