EUROPEAN UNION (WITHDRAWAL) BILL: Effect of losing access to EU single market and customs union
“(1) The Prime Minister must publish and lay before both Houses of Parliament an assessment of the impact on the economy of the United Kingdom, and on each nation, province or region of the United Kingdom, of any unratified agreement (“the Agreement”) between the United Kingdom and the EU under Article 50(2) of the Treaty on European Union which sets out the arrangements for the United Kingdom’s withdrawal from the EU.
(2) The assessment in subsection (1) must so far as practicable analyse the expected difference in outcomes between the Agreement and continued participation in the EU single market and customs union.
(3) The assessment in subsection (1) must be prepared by the Treasury and must include separate analyses from the National Audit Office, the Office of Budget Responsibility, the Government Actuary’s Department, and the finance directorates of each of the devolved Administrations of the methodology and conclusions of the Treasury assessment.
(4) A statute of the kind mentioned in section 9 (approving the final terms of withdrawal of the United Kingdom from the European Union) may not come into effect until the Prime Minister’s assessment under subsection (1) has been—
(a) debated by each House of Parliament, and
(b) approved by resolution of the House of Commons.”—(Ian Murray.)