Civil servants across government departments are preparing for May to trigger article 50 in March, launching the Brexit process.
Penman, who represents senior civil servants – who cannot speak directly to the media – said May appeared to be leading a government that could not cope with any discussion about problems of implementation, as it was interpreted as criticism.
He said: “It is pure politics that is defining the Brexit debate and forcing May to say this is not a big, difficult job, and it is all in hand. Ministers lack the political courage to admit how complex and time-consuming this will be. When anyone pops their head above the parapet – former permanent secretaries, ex-cabinet secretaries, the Institute for Government – and says this is going to take a long time and it’s complex, they are immediately shot down and accused of betraying the will of the people.
“The politics around Brexit are the biggest risk to Brexit. The government is clearly in a situation where they are trying to deny the complexity of it.”