Few repositories of public sector information contain more political dynamite than those in NHS data sets. This week it was NHS staff numbers; next week it could be surgeons' death rates. Earlier this year, the official custodian of the NHS's data raised eyebrows by announcing a special relationship with a commercial firm. At least one competing business has questioned whether a level playing field is possible under the new arrangement.

The case provides an example of the potential conflicts created by the government's policy of earning commercial returns on public sector information - a policy challenged by Guardian Technology's Free Our Data campaign.

The NHS Health and Social Care Information Centre is a special health authority set up last year to act as a single source of official NHS data. Previously, essential statistics about the health service had been collected by many organisations; a bureaucratic nightmare for managers supplying the information and researchers and policymakers wanting to use it. All welcomed the new arrangement, as did private firms selling services based on NHS information. This is a fast-growing market, encouraged by the government's NHS reforms. In January, however, ministers announced that the Health and Social Care Information Centre had struck a deal with one firm in this market, Dr Foster Ltd. The two set up a private company, Dr Foster Intelligence, to sell information derived from NHS data. The information centre invested £12m in the joint venture.

Ministers said the joint venture would "improve use and accessibility of information across the health and care system, in support of the overall aim of giving people more choice and control over health and social care. It will compete with other providers of management information solutions to support better commissioning, choice, quality and efficiency."

Competing companies, however, are worried the new venture will benefit unfairly from the close relationship with the information centre and the investment of the taxpayer. One competitor is CHKS (Comparative Health Knowledge Systems), which supplies hospitals with information to help them compare their performance against their peers. It has written to the Health and Social Care Information Centre seeking assurances that it will have the same access to data as Dr Foster Intelligence. Paul Robinson, marketing director, said the responses had been "positive". However, he added: "Our concern is that no one is monitoring to ensure that it is a level playing field."

The information centre said it publishes a complaints procedure on its website and that any unresolved complaints would go on to the Health Ombudsman.

It adds that, although it is a principal shareholder in Dr Foster Intelligence, "the joint venture will have no special rights to health or social care data, nor any monopoly of supply to health and social care organisations". It said the venture "will stimulate competition in provision of high-quality information to health and social care, and will attract new entrants to the market".

Locus, a body set up to represent businesses relying on public sector information, said any exclusive supplier deal was a cause for concern. Richard Pawlyn, the chairman of the Locus Association, said: "This is symptomatic of the lack of clear guidance from government. The Office of Public Sector Information advocates fairness, transparency and common sense, yet other parts of government promote exclusive supplier deals and create new natural monopolies such as this." He said the association would be asking the Office of Fair Trading, which is investigating the market in public sector information, "to get a hold of these anomalies so the private sector can invest with confidence rather than be wrong-footed and excluded".

A spokesperson for Dr Foster said any preferential treatment "would not be allowed". Tim Kelsey, the chairman of the firm's management board, said: "There is a rapidly emerging and vital market in information in health and social care. DFI, like CHKS, stands or falls on the quality of the service it offers. Open competition is in the best interests of the patient and the client and of the information providers. Nobody, including DFI, has any unfair advantage - nor would we seek it."

See the campaign blog at www.freeourdata.org.uk

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