"Lots of MPs are concerned about their seats and the polls, and they're rapidly forming the view the current management is not performing and will not deliver an election win," one senior Tory MP said.
"The danger is we get a confidence vote by accident because if one MP says 'I'm putting my letter in' others do too'."
The MP added: "I just want him to do better and listen to us. I actually want him to win the next general election, but frankly to please both wings of the party on an issue like this is impossible, and that's where leadership is important."