Railtrack has been ordered by the railway inspectorate to explain why its chief executive, Steve Marshall, has assumed overall control of operations and safety after the dismissal of the company's chief operating officer earlier this month.

It emerged last night that the Health and Safety Executive has issued an enforcement notice against the company saying that its safety case could be unlawful under the new arrangement.

Railtrack could face legal action if it is unable to satisfy the Health and Safety Executive that it has acted within the law.