Britain’s biggest private sector union was hailing a big victory in its battle against Marks & Spencer today after using "cyber warfare" to attack the high street retailer over workers’ rights.

Unite revealed that an internet advertisement highlighting its list of greviances had received more than 12,000 hits in only six hours — more than 30 a minute.

The union is effectively hijacking searches for M&S on Google, the internet search engine.

Anyone typing "M&S" or a list of variations into Google will see a direct link to the Look Behind the Label campaign put together by the T&G section of Unite, alongside normal search results.

A Unite spokesman said: “The number of people viewing this ad shows the power of the internet and how concerned people are about how Britain's major high street retailers behave.”

A source close to M&S said that Google believed the ad infringed its trademark policy and that it may be taken down later today.

The cyber campaign is a stark contrast to the more traditional mass demonstrations, picket lines and work-to-rule campaigns that have defined union protest in the past century.

The cost to the union could be as little as £500, with the ultimate bill depending on how many people click on the link.

Tony Woodley, the Unite joint general secretary, told The Times yesterday: “The power of the internet gives unions the potential to go beyond its membership and reach out directly to millions of people and influence consumers.”

Unite has been in talks with M&S for three months over allegations of a two-tier workforce in companies that supply the chain with poultry and red meat.

The union claims that in an attempt to drive down costs, M&S suppliers are using agency workers on a near-permanent basis, but refusing to grant such workers, often migrants, the same conditions as full-time staff.

Unite also alleges that M&S is not clearly labelling its meat products to hide supplies of cheap imports from Brazil and Thailand, despite the store’s stance as one of the most ethical in the country.

M&S fiercely denies all claims.

Unite is also staging demonstrations at nine M&S stores today.

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