Liz Truss, an education minister, refused to rule out the possibility that teachers, even in faith schools, could face disciplinary action for objecting on grounds of conscience.
Miss Truss said simply that it was impossible to know what the impact of the legislation would be at this stage.
Her admission came in a letter to a fellow Conservative MP, David Burrowes, last month.
Mr Burrowes, a practising Christian, originally wrote to Maria Miller, the equalities minister, raising concerns about the impact on schools of the Coalition’s plans to change the marriage laws.
It followed the publication of a legal opinion by Aidan O’Neill QC, a barrister in the same London chambers as Cherie Blair, commissioned by the Coalition for Marriage, which campaigns against same-sex unions.
Forget about that dead parrot of a question – should we join the eurozone? The eurozone has officially joined us in a newly emerging international organisation: we are all now members of the Permanent No-growth Club. And the United States has just re-elected a president who seems determined to sign up too. No government in what used to be called “the free world” seems prepared to take the steps that can stop this inexorable decline. They are all busily telling their electorates that austerity is for other people (France), or that the piddling attempts they have made at it will solve the problem (Britain), or that taxing “the rich” will make it unnecessary for government to cut back its own spending (America).
The Business Secretary signalled that the Coalition was preparing to unveil a new taxation rate for the better off – possibly at the Autumn statement on December 5.
Pressed on the Andrew Marr programme on BBC1, Mr Cable said that he expected the debate about taxing the well off to be “resolved in the next few weeks”.
The most likely vehicle for the tax raid would be through increasing taxes on people’s homes.
He said: “There needs to be a sense of fairness – better off people in society have got to contribute more. There are arguments around taxation, property taxation – I don’t know where that has got to but it will be resolved in the next few weeks.
“But the principle is right – the people at the top of society have got to pay more.”