The Information Commissioner has ruled that the UK government must name the MPs that belong to the European Research Group, which favours a hard Brexit and is led by Jacob-Rees Mogg MP.
A former adviser to a controversial think tank called the Legatum Institute held unminuted meetings with senior Brexit policymakers.
A controversial think tank called the Legatum Institute has been strongly criticised by charity regulators for failing to maintain "balance and neutrality" on Brexit.
The Eurosceptic Conservative MP Steve Baker has been a director and a trustee of the right-wing Cobden Centre since founding it in 2010 but chose not to declare this in the MPs' register of interests.
Concerns have been raised over the charitable status of a free market think tank that has close links to leading Brexit ministers.