Martin Wakely, head of corporate affairs at Boots, said Superdrug's Solait range mimics its Soltan range in several ways.
'We applied for an injunction on Wednesday. Our case is that the customer could certainly confuse the colours, the name and the whole look,' he said.
But Bill Jones, of Superdrug, said: 'Would you walk into Superdrug, buy our own-brand Solait and think it was Boots's Soltan?'
Geoff Brady, buying and marketing director for Superdrug, says he believes it is more of a battle over prices and market share. Boots, which controls 47 per cent of the pounds 110m sun-care market, refused to comment on his claims.
Soltan accounts for 17 per cent of Boots's total market share and a 200ml bottle of its factor 2 sun lotion sells for pounds 5.79. A similar bottle in the Solait range costs pounds 4.49.
Superdrug is looking to double its own share of the sun-care market from 18 per cent over the next 12 months, with an extensive advertising campaign to launch Solait.
This is not the first time the companies have locked horns. Just before Christmas, Boots, the largest retailer of luxury perfumes, was forced to cut its prices because of competition from shops, including Superdrug, which discounted fine fragrances such as Chanel No 5 and Opium. The fine fragrance market is now being investigated by the Monopolies and Mergers Commission for restrictive practices.
Although both the commission and the Office of Fair Trading say they have no plans to investigate the sun-care market, Mr Brady believes there are similarities between that market and the fine fragrance market because the profit margins for sun-care products and perfumes are both about 50 per cent, adding that this is too high for sun-care products which help to protect people from skin cancer.
If the Boots action succeeds, Superdrug would have to withdraw its Solait range.