Jeremy Corbyn is reportedly determined to avoid pressure to share details of Labour's Brexit plans in the wake of several comments made by key figures in the party.
The shadow cabinet is due to meet on Tuesday for the first time since Theresa May announced a breakthrough in the Brexit negotiations.
Public remarks made by Labour frontbenchers like Sir Keir Starmer and John McDonnell have prompted speculation of a push by the party to maintain single market membership.
McDonnell said the UK could stay part of a "reformed market", maintaining Britain had to keep all options on the table.
Starmer, meanwhile, implied Labour could accept "easy movement" for EU citizens while ensuring trade remained tariff-free.
The shadow Brexit secretary said the party would be willing to accept "alignment" with EU regulations over "divergence" wanted by Tory Brexiteers.
Labour sources told The Guardian the party leader didn't want to spell out a specific position because he didn't want to alienate key voter groups.