Exclusive: Liam Fox tells Tory MPs that customs union will be 'worst of both worlds' in leaked letter

'A customs union - where the UK was obliged to implement the common customs tariff - would allow the EU to negotiate access to UK markets as part of EU trade policy, irrespective of the interests or wishes of the UK. 'It will be able to offer full access to the world's fifth biggest market as part of any EU offer, without the need to balance this access by negotiating on key UK offensive interests.' He said that countries that negotiate new free trade agreements with the EU will have 'automatic access to the UK market with the UK having no reciprocal access'. 'The key question is that if a trading partner already had access to the UK for no cost, why would it be interested in negotiating a further bilateral agreement?'