Reckitt Benckiser is facing an £89 million lawsuit from the NHS after allegedly co-ordinating updates of GP prescription software so that the cheap version of its Gaviscon heartburn medicine no longer appeared.

The company has been served with High Court papers, which also state it delayed steps to allow generic versions of Gaviscon to appear on the market. It denies the accusations and has said it will "vigorously defend" itself.

When branded medicines' patents have expired and a generic name has been assigned, GPs can use their prescription software to search for the brand and provide patients with an 'open' prescription that refers to its generic name. Pharmacies can then choose which product to provide.

The NHS lawsuit alleges that Reckitt "co-ordinated the updating of computer-based subscribing systems used by GPs", the Financial Times reported, so that only its more expensive Gaviscon Advance product was visible when doctors attempted to prescribe medicine for heartburn sufferers.

Reckitt declined to comment further.

The lawsuit follows a £10.2 million fine issued last week by the Office of Fair Trading, which said Reckitt Benckiser had abused its dominant position "with the intention of limiting pharmacy choice and hindering competition from suppliers of generic medicines".

The OFT investigation found that Reckitt had withdrawn packs of Gaviscon Original, the cheaper product, from the NHS prescription channel after the product's patent had expired but before the publication of the generic name for it. The intention was for more prescriptions to be issued for Gaviscon Advance, because that product is still patent protected and has no alternative generic equivalent, the OFT stated. Reckitt agreed to settle early and reduced its fine from £12 million.