Marks & Spencer plans to join European monetary union (EMU) even if rest of the UK opts out in 1999.

The retail giant is now forging ahead with a pan-European conversion programme, starting with the upgrade of cash register technology, said finance director Robert Colvill.

M&S hopes to reduce the financial burden of EMU modifications with a carefully planned series of upgrades in its 31 stores in mainland Europe.

In the UK, M&S currently operates 285 stores. Eventually, these too will accept euros and provide dual price displays - even if the UK opts out of the first round of EMU.

A spokeswoman said: 'The latest software upgrade will support EMU and provide dual currency display even if the UK opts out. Advanced till technology will make it much easier for the potential EMU move.'

In May, M&S chairman Sir Richard Greenbury told a Commons committee that, at worst, EMU would cost the company u100m. This included replacing tills, new hardware, software and training.

This week, M&S told Computing that the cost was likely to be between u10m and u50m - because the conversion would be phased in gradually.

'If the changes for euro currency are not required to be fully implemented until early in the 21st century, then a rolling project will give us plenty of time and will lessen the overall expense,' Colvill said.

An in-house team, together with several consultants, has started work on the EMU project. Work on cash register upgrades has already started in some stores.

After ill-judged diversification into the US during the 1980s, M&S now has aggressive plans for European expansion.

The British Retail Consortium claims EMU will cost up to 3% of retailers' turnover. M&S turned over #7.2bn in the year to March 1996.