Household goods giant Reckitt Benckiser was accused today of abusing its dominant position in the supply of heartburn medicines to the NHS.

The Office of Fair Trading (OFT) alleges that Reckitt sought to restrict competition to its Gaviscon treatment by offering family doctors only a more expensive version of the product when they searched prescribing software.

Doctors use software to search for well-branded products and then provide patients with an "open" prescription that lists its generic name.

This allows pharmacies to choose whether to dispense the brand or a cheaper rival, at considerable cost savings to the NHS.

In a statement of objections, the OFT said Reckitt deliberately delisted a sister product just before cheaper generic rivals joined the list.

The timing of this meant that an NHS doctor searching for Gaviscon would instead bring up its Gaviscon Advance Liquid - a patent protected version that did not have an "open" prescription which would have allowed generic rivals to be shown to GPs, according to the OFT.

Simon Williams, senior director for goods at the OFT, said: "This case raises significant and complex competition issues relating to the supply of prescription drugs to the NHS."

The OFT said it would wait for a response from Reckitt before giving a final verdict on whether it believes competition law has been broken.

If found guilty, Reckitt could face a potential fine of up to 10% of its worldwide turnover, which stood at £7.75 billion in 2009.

But Reckitt said it believes it "competes fairly and within the letter and spirit of the law in all of our operations".

The group added: "Gaviscon Advance is a second generation product, superior to Gaviscon Original.

"Gaviscon Advance was launched to provide patients with effective and long-lasting relief from heartburn and indigestion.

"Reckitt Benckiser will now review the OFT statement and respond accordingly."