Marks & Spencer was yesterday accused of telling some staff they are to be made redundant amid reports that more than 1000 job are to be axed.

The UK's biggest fashion retailer, which employs 70,000 staff, declined to comment officially on a report it was poised to axe staff in its stores and head office when it unveils a Christmas trading update today.

However an employee at the firm's Aberdeen store claimed she and two colleagues had already been told that they are to lose their jobs, while a part-time worker in London said she had been told her job was finishing on Friday. If true, this could be illegal under employment law.

The GMB, which is seeking urgent talks with Marks & Spencer, warned that the company could face a series of employment tribunal cases if it announces a large number of redundancies. Union officials said earlier this year it feared the firm was gearing up to make big job cuts following the case of a worker who was sacked for leaking details to the media of planned changes to redundancy payments.

The union's legal officer Maria Ludkin said: "This proves that M&S has already started to identify who is going to go.

"If these reports are correct, M&S have to give 90 days' notice for consultation. If M&S tries to take a short cut and treat each shop as a separate workplace, and thereby give only 30 days' notice, GMB will not hesitate to take employment tribunal cases for a 90-day protective award."

Sales over the festive period are believed to have fallen by 8.5%. The firm has already been forced to cut investment to reduce its £3bn debt, as well as making workers' redundancy packages less generous. Branches of the retailer held two days of 20% discounts in the run up to Christmas, a move which could have contributed to a decline in overall sales.

But, according to one insolvency expert, the job cuts are "sensible", and showed that managers were looking to the future and planning for an extended period of financial strife rather than simply reacting to a few weeks of poor trading.

Nick Hood, from Begbies Traynor, said: "If a business is suffering a downturn in sales, particularly if its focus is in certain areas - and it looks as if the downturn is worst in fashion - then I would expect a management team to be looking at the business and thinking how to cut back.

"What it reflects is that Marks & Spencer are making a judgment that this is not going to be a temporary downturn but will last through 2009 and into 2010.

"If it is a short-term thing then you don't want to get rid of key staff because it is expensive to replace them. But if you decide it will be long term then it is very simple. At the end of the day you have to match your costs with your revenue."

Mr Hood predicted that between 10 and 15 high street chains would go under by the end of this month, adding that conditions for retailers were getting worse, especially since it would be difficult for them to move away from discounting.

Clothing retailer Next said yesterday that its sales had dropped 7% in the six months to Christmas Eve, while Debenhams announced a 3.3% drop in sales.

However both sets of figures were better than feared, and the firms' shares rose sharply.

Staff at Marks & Spencer's headquarters in Paddington Basin, London, said the redundancy reports had made workers feel "anxious".

One staff member, who did not want to be named, said: "We haven't been told anything officially but everyone's talking about it. We only really know what we heard in the news. We don't know who might be sacked."