The biggest Names organisation is to vote against Lloyd's at the EGM next week.
The Association of Lloyd's Members (ALM) is advising its 5,400 members to vote against the Chairman's Strategy Group (CSG)proposals on 12 September.
The ALM is in favour of the central proposal to turn Lloyd's into a franchise, but is unhappy about others.
The two main objections are to creating a new Lloyd's Act, and the abolition of the Lloyd 's Regulatory Board and the position of director of regulation.
A contentious issue is the style of the EGM vote - it is a broad resolution to approve implementing the proposals "in such manner as it shall think appropriate ".
ALM chairman Michael Deeny described this as "a blank cheque to approve a curate's egg".
Deeny also reiterated concerns over the profitability of international corpo- rates, saying this issue had not been addressed by the proposals.
The ALM was at pains to point out it had previously tried to iron out differences with Lloyd's by negotiating in August and said it had never advised its members to oppose a Lloyd's vote before. In a statement Lloyd's said it was disappointed by the ALM 's opposition to reforms it believes must go ahead.
"The ALM is seeing problems where none exist. Its opposition to the reforms is based on a series of imaginary hypothetical threats," it said. Last week, Lloyd 's deputy chairman John Coldman urged members to back the modernisation proposals.
He said that a Lloyd's riven by internal tensions would not inspire confidence and advocated unity from the market's financial backers.
The ALM said it still expected the EGM vote to be carried "overwhelmingly".
But it said its opposition was important because for many of the proposals to take effect Lloyd's would have to pass byelaws that would be open to challenge by members calling an EGM.