By Georgie Keate
Nick Clegg has claimed that even the prime minister was not aware of Michael Gove's controversial plans to bring back O levels.
The deputy prime minister is staunchly against the reforms and has stressed that they cannot go through without backing from the Lib Dems.
"This has not been subject to collective discussion in government. Neither myself nor the prime minister were aware of it," he told BBC Radio 4's The World at One programme.
The proposal, which aims to axe GCSEs and replace them with old-style O levels for brighter pupils and the simpler CSEs for the rest, was leaked to the Daily Mail yesterday.
The Lib Dems argue the system will create a "two-tier" education system with some children "cast on a scrapheap".
"If Michael Gove wants to turn some of his ideas into government policy he's entirely entitled to put that forward for wider discussion," Mr Clegg told the BBC.
"By definition in a government if you have collective agreement, and particularly in a coalition, it requires support from all sides."
The Department for Education admitted to not alerting Mr Clegg about the proposals but have claimed they can press ahead without Lib Dem support because legislation is not needed.
Senior Conservatives like Kenneth Baker and Graham Stuart have also spoken out against the reforms, however, while justice secretary Ken Clarke has said that he and Mr Clegg will chair the cabinet committee that will scrutinise the proposals.
Mr Gove's education plans will be published around the same time as Mr Clegg's House of Lords reform bill, signalling a contentious time for the coalition.