The company originally hoped to launch the service, which will run direct from Wearside to the capital three times a day, on December 10.

Grand Central has agreed the purchase of three high-speed trains from Porterbrook Leasing.

But these are due to undergo a full refurbishment and re-engineering programme to have them ready for main-line duties in 2007, with more than £5million to be spent on the stock over the coming months.

Now a question mark hangs over the start date of the service as the company works to find trains to plug the gap between the planned launch date and the completion of work on the trains already secured by Grand Central.

Ian Yeowart, managing director of Grand Central, said that the long-term future of the service is now secure.

"The long-term was the priority as there is no point in starting a service that we wouldn't be able to continue six months down the line – the service is now guaranteed for the next 12 years," he said.

"We are working hard to secure short-term suitable rolling stock, and in particular colleagues at National Express, Maintrain, Porterbrook Leasing and Angel Trains are trying to ensure stock can be made available for a start prior to our own trains coming out of works".

Mr Yeowart said that there was every chance that the service would still start on time, but the launch date may be delayed until early 2007.

Grand Central is expected to make a further announcement on the start date for the new services in the next few days after further discussions have taken place.

Meanwhile, financial experts fear rival train company GNER could soon go off the rails.

It was reported at the weekend that the East coast mainline operator would have no choice but to give up what is left of its 10-year franchise and hand over day-to-day running of the route to the Government, possibly by the end of the week.

Department of Transport officials have confirmed they already have a plan in place to take over control of the route should GNER decide to back out of its £1.3billion agreement.

The rail firm's parent company Sea Containers has debts of £340million and has only six days left to find £60million owed to creditors. If they don't find the money the company could be forced into liquidation, which could mean trouble for GNER.