The EU decision early this month that sufficient progress had been made in the brexit stage 1 negotiations to proceed to stage 2 was predicated on the May government, in effect, recognising that the UK will continue to adhere to adherence to customs union (CU) and single market (SM) processes during the anticipated two year post-March 2019 transitional period, so staving off the imposition of a hard Eire/NI border.
Many in her party are still wedded to the illusion that it can be avoided without continuing de facto continuing SM and CU membership post 2019, or find it convenient for their own purposes to pretend that is the case.
In response, Keir Starmer(KS) has suggested that the UK is moving to a Norway European Economic Association (EEA) arrangement, implying continuing FOM, UK membership contributions, and fealty to ECJ jurisdiction. Meanwhile John Mcdonnell(JM),while also highlighting the advantages of continuing adherence to SM, rules out continuing FOM.
Quite likely both front benchers are flying mutually understood kites, but JM risks mimicking the hubris of the government brexit approach by holding out that the UK can maintain the benefits of the SM, while ditching free movement.
As suggested in a hybrid option where the UK proceeds into the medium term on the basis that it will proceed to negotiate a CFTA while maintaining adherence to CU and SM processes, appears at present most likely as that would avoid the economic damage of a disorderly exit, but would allow the political can to be kicked beyond a 2022 election.