Parliamentary Under-Secretary of State
A Parliamentary Under-Secretary of State (also called a Parliamentary Secretary, especially in government departments not headed by a Secretary of State) is the lowest of three tiers of government minister in the government of the United Kingdom, immediately junior to a Minister of State, which is itself junior to a Secretary of State.
The Ministerial and Other Salaries Act 1975 provides that at any one time there can be no more than 83 paid ministers (not counting the Lord Chancellor, up to 3 law officers and up to 22 whips). Of these, no more than 50 ministers can be paid the salary of a minister senior to a Parliamentary Secretary. Thus if 50 senior ministers are appointed, the maximum number of paid Parliamentary Secretaries is 33.
The limit on the number of unpaid Parliamentary Secretaries is given by the House of Commons Disqualification Act 1975 ensuring that no more than 95 government ministers of any kind can sit in the House of Commons at any one time; there is no upper bound to the number of unpaid ministers sitting in the House of Lords.
The position should neither be confused with the Permanent Secretary which is the most senior civil servant in a government department (officially also known as the Permanent Under-Secretary of State), nor with a Parliamentary Private Secretary (an MP serving as an assistant to a minister entitled to directly relevant expenses but no further pay).
Of his tenure as an under-secretary in Macmillan's 1957–1963 Conservative government from the Lords, the Duke of Devonshire noted "No one who hasn't been a Parliamentary Under Secretary of State has any conception of how unimportant a Parliamentary Under Secretary of State is