The public's health is being put in danger by a lack of planning for possible biological attack, the Conservatives have claimed.

The shadow health secretary, Dr Liam Fox, warned on Monday that the new Health Protection Agency has not made full contingency plans for a possible terrorist attack on the UK.

He said that a leaked internal report criticised several key aspects of the government's proposals which would replace the Public Health Laboratory Service.

The idea had been a central proposal of a review published by the chief medical officer last month.

"Ahead of the Curve" had called for one coherent government body to take over responsibility for public safety on April 1.

Fox highlighted sections of the report where concern was expressed that there was not enough time to transfer laboratories to the PHS without potential damage to the public health.

He claimed the government had chosen the wrong time to push through change and that proper preparations had not been made.

"At this time of heightened threat, the government should be bringing in the new arrangements only when they know that standards will not be compromised," he said."As things stand there is a serious danger that NHS staff will be distracted from the roles that they need to be concentrating on, and that an expert service will become fragmented. Too much change will occur too quickly. Reforms need to take place over a longer time frame."

The Department of Health challenged Fox's claims, saying the new agency was capable of delivering a coherent and unified health protection service.

"This move can only strengthen this country's ability to respond effectively to a chemical, biological or radiological incident," said a spokesman.

"We have built in safeguards from the start of this process to ensure that all public health functions are protected as the agency is created. It is in addition to this as part of a normal business planning process that we have carried out a detailed risk assessment. An action plan was drawn up to address any risks identified through that process."