Retail giant Marks & Spencer (M&S) is to extend item-level trials of radio frequency identity (RFID) technology from nine to 53 of its UK stores.

The next phase will start in spring 2006, and see the company expanding use of the technology from men's suits to other products with availability issues - those with complex sizing structures such as bras, which have 68 different sizes.

M&S will also investigate how the technology can improve services to customers by integrating labels containing the RFID chip into traditional paper barcode labels that already contain information about the size and cost of an item.

But the tags will be passive, meaning they do not transmit any information unless a scanner is passed over them.

'RFID may have the potential to significantly improve product availability, which research has shown is a key issue for customers,' said a spokeswoman.

The retailer has chosen BT to work with on the trials. 'BT has been selected as the main contractor on the trial, providing managed IT development, and ongoing deployment and maintenance of mobile RFID readers in-store alongside tag and reader supplier Intellident,' said the spokeswoman.

The retailer will use mobile scanners - which can read RFID labels 20 times quicker than traditional barcode labels - in phase two of the trial, allowing M&S to speed up stock checks.

At the end of each day, stock on the shop floor will be scanned. Data collected will be compared with information in a central database containing each store's stock profile, to trigger replenishment orders.

'M&S is being pretty pragmatic about this move to extend its RFID trial,' said Neil Macehiter, partner at analyst Macehiter Ward-Dutton. 'And it's clearly oriented towards cost benefits by merging the barcode and RFID label into one.

'The issue is not the device itself, though. It will be how well the back-end systems cope with actually exploiting this more detailed information.'

The spring 2006 trial will be completed by the summer. The clothing trials supplement tests on four million returnable food produce delivery trays that started in 2002.