The minister for political and constitutional reform, Mark Harper, launched the 12-week consultation into lobbying in January, but excluded in-house lobbyists, leading many to suggest the consultation is 'fundamentally flawed'.
However, insiders have suggested that Harper is now warming to the idea of including in-house lobbyists.
He has consulted figures such as Airport Operators Association chief executive Darren Caplan, who said that excluding the 80 per cent of lobbyists who are in-house would be 'unfair'.
This shift is understood to worry several organisations that have huge lobbying firepower, such as the Confederation of British Industry and a body that it administers, the Trade Association Forum.
The forum's manager, Linda Cavender, told PRWeek: 'We do believe that trade associations should be excluded. We do exactly what is says on the tin - it's less clear with lobbying consultants.'
Cavender added that she believed that the idea of a statutory register in general was disproportionate to the 'perceived problem'.
Her call was seconded by DG of the Institute of Economic Affairs Mark Littlewood, who said a register should only include agencies.
While the CBI declined to comment, PRCA chief executive Francis Ingham said: 'The CBI is arguably the country's biggest lobbyist. When I worked there, the level of access it had to ministers was astonishing - Digby Jones would regularly phone ministers without notice.'
A Cabinet Office spokesman denied that Harper had made any decision on including in-house consultants.
Harper is understood to have initially thought that a register including in-house lobbyists would be over-long, but a suggested way around this would be to make it retrospective, for instance by focusing on the activities that were carried out over the previous three months.
