Foreign academics at one of the country's top universities have reportedly been banned from advising the Government on Brexit because they are not British nationals.
The claims emerging from the London School of Economics (LSE) have been branded "utterly baffling" by Nick Clegg.
Sara Hagemann, an assistant professor at LSE's Europe Institute, said Government representatives told her they will no longer take advice from her or her non-UK colleagues.
Mr Clegg, former Lib Dem leader and now its European Union spokesman, said: "It is utterly baffling the Government is turning down expert, independent advice on Brexit simply because someone is from another country.
"This is yet more evidence of the Conservatives alarming embrace of petty chauvinism over rational policymaking."
Steve Peers, a professor of EU law at the University of Essex, said: "What kind of know-nothing nativist Government rejects the expertise of all non-citizens?"
The move is reportedly due to concerns over sensitive data being exposed during Brexit negotiations.
Ms Hagemann tweeted: "UK govt previously sought work & advice from best experts. Just told I & many colleagues no longer qualify as not UKcitizens #Brexit"
A spokesman for LSE said: "The UK Government regularly calls upon LSE's world-class academics for their advice on a range of issues.
"We believe our academics, including non-UK nationals, have hugely valuable expertise, which will be vital in this time of uncertainty around the UK's relationship with Europe and the rest of the world.
"Any changes to security measures are a matter for the UK Government."
It comes just days after Home Secretary Amber Rudd outlined proposals to make British firms publish lists of their foreign workers, a move which has prompted criticism from businesses and her own brother.