The Department of Health’s most senior civil servant has warned that publishing the risk register for the government’s health reforms would have an “insidious” effect on the workings of government.

Una O’Brien, the DH’s permanent secretary, told an Information Tribunal that publishing the register could “seriously affect the quality of advice given to ministers.”

She argued that civil servants might “tone down” similar documents because of how they might be “viewed externally."

The DH is fighting a ruling from the Information Commissioner that it should publish the register at a tribunal that is expected to take two days.

In November, the commissioner concluded there was a “very strong public interest” in disclosing the register.

However, health secretary Andrew Lansley has argued that it would be “completely misleading” to publish the document, since it was intended as an “internal mechanism” and changes have been made to the bill since it was drawn up.

Campaigners against the latest reforms, including the Labour party, the BMA and some of the royal medical colleges, have been calling for the register to be published.

Risk registers drawn up by the four cluster strategic health authorities have shown they are worried about organisational instability, conflict in the new NHS market, overspending, and reduced patient safety. NHS North of England has also identified risks to its IT and information plans from the reforms.

The government has refused a number of Freedom of Information Act requests to disclose the main risk register.

The Information Commissioner ruled it had been wrong to do so because “the public interest in maintaining the exemption does not outweigh the public interest in disclosure.”

However, the DH is fighting the decision at the tribunal, and could take the case to the High Court if it loses.

The battle is taking place as the bill returns to the Commons, and the Liberal Democrats are preparing to debate the reforms at their spring conference.

Disquiet about the ‘Liberating the NHS’ reforms at last year’s Lib Dem spring conference helped to force the government to ‘pause’ the passage of the bill through the Commons.

It set up a ‘listening exercise’ led by the NHS Future Forum to try and allay concerns.

But an increasing number of professional bodies have come out against the bill as it has been further amended during its passage through the Lords over the past few months.

Lib Dem activists are preparing an emergency motion for next week’s spring conference, saying the bill should be “withdrawn or defeated.”

But Prime Minister David Cameron has come out fighting for the legislation, insisting it will increase choice for patients while integrating services and putting power into the hands of GPs.