If grey fleet was included when calculating fleet size, many companies would find their vehicle numbers doubling overnight.

Research as part of the Fleet200 has revealed that the ‘hidden’ grey fleet within companies almost matches the traditional car and van fleet combined.

Within the Fleet200, the total grey fleet accounts for 420,924 vehicles. This almost equals the half a million company cars and vans operated by member companies.

Grey fleet drivers are likely to reclaim the costs of business mileage using the Government-approved mileage allowance payment, which is currently set at 45 pence per mile.

Typical annual business mileage for a grey fleet driver is 6,000 per year, which equates to a potential bill for mileage payments of £1.1billion across the Fleet200.

There are more than 250,000 cash-for-car drivers within the overall grey fleet, plus an estimated 150,000 ad hoc drivers who occasionally use a private vehicle for business purposes.