A Coalition dispute erupted yesterday over a Liberal Democrat minister missing a Commons votes on welfare cuts.
Sarah Teather, the Children's minister, has previously criticised the move to impose a £26,000 cap on the annual amount of benefits that families can claim. She was absent in Sheffield on "ministerial business" when MPs voted on the policy last week.
Conservative MPs have called for her to be sacked and David Cameron's spokeswoman said her absence had been cleared in advance. He told MPs: "She supports Government policy, as all Government ministers do."
Later a Downing Street source said: "If she speaks out again, it will be curtains for her."
A Liberal Democrat source countered: "That is just nonsense. She is a very highly valued member of the Government. This is being whipped up by the Tories."
Ms Teather, who is regarded as on the left of the Liberal Democrats, insisted she backed the Government's agenda, but did not explicitly say she supported the benefits cap.