West Ham were forced to bin plans to wear a specially-designed kit in the FA Cup after an embarrassing administrative mix-up.

The Hammers unveiled a commemorative 'Thames Ironworks' navy-blue outfit in August and told fans it would be 'worn during our FA Cup campaign'.

But there was no sign of it as they crashed out in the third round at the hands of Manchester City on Friday night, with their regular home kit worn instead.

West Ham released an FA Cup kit - a tribute to Thames Ironworks - before the season began

But they did not wear it against Manchester City in the FA Cup third round on Friday night

And Sportsmail can reveal club chiefs believed they had the sign-off from the FA to wear the special shirts at the start of the season — only to later be told it contravened the governing body's regulations.

An source close to the FA said the problem stemmed from a commercial issue with the shirt. There are strict guidelines over the size and prominence of sponsors' logos on teams' shirts.

The kit, which featured a Union Jack detail harking back to West Ham's forerunners Thames Ironworks FC and a blacked-out glossy logo of sponsor Betway, is now set to be left unworn apart from when it was used in a pre-season friendly against Juventus back in August.

The foul-up has caused frustration among supporters, who had paid up to £55 for the shirt alone. The full kit cost up to £90 and sold out within weeks of its launch in the summer. It remains on sale after stock was replenished.

The shirt, which was sold to supporters for £55 and remains on sale, cannot be worn

West Ham vice-chairman Karren Brady reacted to questions about why the Ironworks kit would not be worn, writing on Twitter that it was a 'shame' and that club chiefs 'LOVE that kit'.

West Ham season-ticket holder and Twitter user Richard Wenn wrote: 'Well shouldn't this have been checked with the FA before advertising that it would be worn in the FA Cup? #FalseAdvertising.'

Another, David Cullinane reacted by saying: 'Great! Waste of time that was.'

West Ham have not issued any advice to any buyers and it seems the kit will now not be worn again.

It did feature as West Ham lost 3-2 against Juventus in a friendly to officially open the London Stadium on August 7, with Andy Carroll scoring twice, but it now looks to be consigned to the laundry basket.