Both sides have now adopted the idea of a royal charter - a formal document used to set up bodies such as universities and the BBC - but there are key differences between the two plans.
Both the prime minister and the two other parties agree on the concept of a royal charter, a formal document used to establish and lay out the terms of an organisation, for example the Bank of England or the BBC, that cannot be changed without government approval.
Royal Mail said it '"did not recognise" the document and said it did "not reflect Royal Mail's policy, strategy or position in relation to the current dispute with the CWU".