Contingency plans are being drawn up to ensure patients can continue to receive vital medicines from Europe after Brexit, ministers have said.
Lord O'Shaughnessy said the Government's aim was to maintain easy access to drugs and medical devices from the European Union as part of the Brexit deal sought by Theresa May.
But Lord O'Shaughnessy said work was ongoing to protect patients and businesses should the talks with Brussels collapse.
He said that the work was "not at the point where that's something we are able to share" in public.
Ministers had also commissioned consultants to produce an analysis of the supply chain for medicines across the EU to determine the extent of potential problems.
Health Select Committee chairwoman Sarah Wollaston said MPs had been given "very stark warnings" that a no deal Brexit could result in people turning up at pharmacies and "essential - not just everyday, but essential medicines or supplies - just not being available because of the complexity of the supply chains".
Lord O'Shaughnessy told the Health Select Committee that the UK wanted to negotiate a "deep and close relationship with the European Medicines Agency to replicate the arrangements that we have now, albeit obviously on a different legal basis".
The Government also wanted "very swift and frictionless customs arrangements".
But he said: "We have to prepare for all eventualities including the one that we don't want as well as the one that we do want."
He told MPs: "In terms of a no deal scenario, we have got to make sure that whatever happens two things are true: firstly patients aren't disadvantaged in terms of their access to medicines, devices and other things and secondly that there are no additional burdens and barriers to industry so that they are happy to bring their products to the UK.
"There is work going on, it's going on with other agencies across government to work out what that looks like, but we are not at the point where that's something we are able to share."