However, the number of responses to the integrated transport policy discussion document - more than 6,000 - resulted in the Department of Environment, Transport and the Regions announcing that it would be delayed until May. Now it is likely the white paper will not be published until late May at the earliest, but more likely not until June or July.

Two leading industry sources said this week the Department's spring publication date was unlikely to be met and they expected the white paper to be published in June or even July.

A DETR spokeswoman said the Department was sticking to its spring deadline, but a report in the Financial Times suggested the white paper would not be published until mid-June because of the complexity of the issues involved and the difficulty of resolving conflicting interests.

It is understood that while the white paper will contain the framework for a future transport strategy much of the detail - including changing the company car tax system from one based on business mileage to one based on private mileage - will be contained in a series of supplementary papers, some of which could be published in the weeks and months after the white paper.