Thousands of screws used to secure the decking on Weston-super-Mare's new £51 million Grand Pier may have to be taken up and replaced – because they are the wrong size.

It is understood the error was discovered during an inspection of the new decking which was laid around the pavilion last month.

Engineers said the screws used to pin the decking into place are not of the right specification and around 40,000 of them could have to be taken out.

Structural engineers have been brought in to assess the problem and are currently preparing a report on the decking.

It is understood that although the decking will be able to take the weight of pedestrians, there are concerns about whether it will be able to safely take the weight of heavy vehicles.

Main contractors John Sisk and Son is waiting to see the result of the report before making a decision about whether the screws need to be replaced.

Work to rebuild the pier started in April 2009 but the project is now two months behind schedule after being hit by a number of delays.

The news will come as another blow to the Michaels who estimate they are losing a million pounds a month in revenue during the peak summer months because the pier is closed.

Mr Michael refused to comment on the screw size being wrong, but has previously said: "Structural engineers are looking into the design of decking to see if it meets the requirements and if, as I fear, it does not, it will have to be stripped and re-done.

"I am bitterly disappointed at the continued delays on the project."

This is the latest in a series of major blows to the project to rebuild the pier, which was destroyed in a fire in July 2008.

They have also recruited around 300 people to work on the attraction either full time or part time – the majority of whom are still waiting to start their new jobs.

Although a completion date has yet to be announced the Michaels believe it is "imminent".

No one at John Sisk and Son was prepared to comment on whether the wrong screws had been used when laying the decking, but admitted the entire project was a complex one.