I understand that some MPs in the government parties are considering the possibility of pushing through plans to transfer tax-varying powers to Wales without a referendum because of what they see as Labour 'intransigence' on the issue. The current plans require a referendum before any such move.
If you want to catch up on the row, and see why Labour thinks the proposal is a politically-motivated 'trap,' click here, here and here. The other parties believe Labour is angry that devolution has been taking out of its hands for the first time.
One Conservative source said that 'intransigence' raises 'serious questions about the way in which fiscal responsibility can be imposed on the Welsh Government' and used the word 'imposed' deliberately. It's controversial even to suggest and is a sign of exasperation on the government benches.