Ministers to decide whether to veto ruling that it should publish assessment of impact of the new Health and Social Care Act

The cabinet will decide on Tuesday whether the government wants to veto a ruling that it should publish a full and frank assessment of the impacts of its Health and Social Care Act, which was passed in March.

Ministers plan to discuss a possible appeal or veto amid confusion over whether they might have missed the deadline for both, following a ruling by the information tribunal last month that the risk register must be made public.

The disagreement over dates – which relates to whether the 20-day deadline for a veto and 28 days for an appeal include weekends and bank holidays – is awkward for a government already embarrassed by confusion over another deadline in the Home Office's continuing efforts to deport the radical cleric Abu Qatada. That dispute has become part of the litany of criticisms rolled into claims that the coalition has become an "omnishambles" – a tag it appears to be finding it hard to shake off.

The information tribunal announced in March that it rejected an initial government appeal against the information commissioner, and published its full ruling on 5 April, setting out that the Department of Health should publish the risk register.

Under the tribunal's rules, the government has 20 days to exercise a veto – a drastic step it has taken only three times in more than a decade – 28 days to lodge an appeal, or 30 days to publish the information. After a day of confusion, lawyers for the MP who first lodged the request for the risk register to be published suggested that the 28 days to appeal did include weekends and bank holidays, and so had passed. But the government said the 20 days to veto the ruling included only working days, and so the deadline was Tuesday. A third option for the government is to launch a late appeal if it can convince the tribunal that there were good reasons for the delay.

Either way, the decision is likely to be controversial, despite the original health bill having passed into law, because Labour has continued to keep up its strong opposition while ministers try to get the necessary secondary legislation passed.

John Healey, the Labour MP who made the original request for the risk register under the Freedom of Information Act, said an application for a veto would be "a desperate act which will backfire badly".

"People will suspect ministers of burying this bad news on the eve of the Queen's speech," added Healey. "It adds to the aura of political panic, and will only fuel doubt and distrust about the government's NHS plans. There must be some very big risks in the government's NHS reorganisation for ministers to override the law."

Government officials, however, emphasised that any veto or appeal would be because they did not want a precedent set for publishing "confidential" advice from civil servants to ministers about prospective policies, which includes "worst-case scenarios".

"Our position on this hasn't changed," said one senior official. "The idea of a risk register is they are frank information for minsters on which to make decisions. If, instead of being confidential, risk registers are now effectively public documents, the nature of the advice would inevitably be different and not necessarily the advice we would require."