It was sighs all around at Asda House on Thursday when a five-day strike by warehouse staff, due to have started yesterday, was called off.

But although the multiple managed to avoid major disruption over one of the busiest sporting weekends of the year, it was something of a Pyrrhic victory and the GMB's general secretary, Paul Kenny, was quick to hail the unions as the real winners in the long-running dispute over pay and collective bargaining rights.

It will certainly be seen as evidence that the unions are growing in power. And Asda is not the only multiple that should be alert to the threat. The Grocer predicted earlier this year that the whole grocery retail sector was heading for a showdown with the unions (The Grocer, 14 January). In short, everyone needs to have contingency plans in place should a strike threat materialise.

Asda claims it was fully prepared for the strike. A spokeswoman says it planned to serve its stores from its non-organised depots. It would also have moved buffer stocks into back-of-store storage areas previously used for bulky non food items. Perishables such as milk, eggs and bread, as well as locally sourced goods, would be unaffected by a distribution strike, she claims, as they are normally delivered directly to stores.

However, some observers suggest that Asda exaggerated the comprehensiveness of its contingency plans and argue that it would have lost millions from the extra labour, delivery and stock carrying costs it would have incurred. The Asda spokeswoman would only say: "We would have taken action to make sure that consumers were not affected, but I can't go into detail, as we do not want to reveal those plans to the other side."

However, the GMB, which had accused Asda of driving a "coach and horses" through employment law, claims that Asda's plan included hiring agency workers to fill in for employees who would be sent to cover for striking workers. This, says the union, would have been a violation of the Conduct of Employment Agencies & Employment Business Regulations 2003.

Asda denies it was planning such a move. "We use agency workers every day," says the spokeswoman. "But we have no more agency workers now than we did at this time last year. We are well aware of the law and would not have been breaking it."

The GMB also claims that Asda was trying to move agency workers onto its full-time payroll after as little as two weeks, whereas it typically takes 13 weeks. A GMB spokesman says: "We believe that Asda was pre-loading workers into depots. They hired many agency workers who were sitting around with nothing to do. We have asked the agency and it says that they are now Asda employees."

Asda denies this as well. "As far as I am aware we were not doing any such thing," says an agency spokeswoman. "But even if we were, if that is legal, what is wrong with it?"

The CEAR 2003 does not bar companies from taking on full-time employees during a strike action to cover for striking workers, but Andrew Taggart, a partner in Herbert Smith's employment law practice, notes that the full implications of such a move have not been tested in a court of law.

The good news is that Asda had a contingency plan at all. Fraser Younson, partner at McDermott Will & Emery, says: "Surprisingly, most companies don't have contingency plans, but they should. The duration of these things is a relatively short period and the learning curve is steep, so companies should have plans in their drawer ready to use." n