Ghosh will depart in September, ending a 33-year career with the civil service. Before moving to the Home Office at the end of 2010, she served as permanent secretary at the Department for Environment, Food and Rural Affairs.

She said: ‘I have been privileged to lead the Home Office and feel very torn about leaving. But the work of the National Trust is something that is very close to my heart and this was a rare opportunity to lead a major voluntary organisation, which I could not allow to pass by.’

Ghosh’s departure elicited tributes from Home Secretary Theresa May and civil service head Sir Bob Kerslake.

May said: ‘I am very grateful to Helen for her support, wise counsel and outstanding leadership of the Home Office during an extremely busy period for the department.’ She added that the National Trust was ‘very lucky to have secured her services’.

Kerslake said: ‘As permanent secretary at Defra and the Home Office, Helen has delivered extraordinary change including departmental reform, the independent UK Border Force and support for the successful London Olympics.’

Helen Kilpatrick, director general of the Home Office’s financial and commercial group, will lead the department as interim permanent secretary until Ghosh’s replacement is appointed.