Actor Maureen Lipman, who has supported Labour for about 50 years, has said she will no longer vote for the party while it is led by Ed Miliband.
In an article in Standpoint magazine, Ms Lipman condemned Mr Miliband for supporting a House of Commons motion to recognise Palestine as a state.
“The world is exploding around us. Isis is beheading our civilians while raping and pillaging across Syria and Iraq. Presidents [Vladimir] Putin and [Bashar] Assad are playing such heavy-handed games that we don't know which rebel group to support,” she said.
“Hong Kong may be about to see a replay of Tiananmen. Islamist terrorism in every spot on the globe and if one Jew had been responsible for any of those bombings, there would, I am afraid to say, have been another Kristallnacht.
“At this point in our history you choose to back these footling backbenchers in this ludicrous piece of propaganda?”
Ms Lipman, who said she had liked former Labour leaders such as Neil Kinnock and Tony Blair, contrasted support for UK air strikes on Isis in Iraq with opposition to Israeli air strike on Gaza in response to rocket fire into Israel.
“May I remind you that no one is tunnelling into Dover or sending rockets into Coventry, yet we seem to have every right to bomb the living daylights out of Iraq… Conclusion: one law for the Israelis, another law for the rest of the world. Plus ca change,” she said.
Ms Lipman said she would vote for “almost any other party” until Labour was once again led by “mensches” – meaning people with integrity and honour.
“I rather liked David Miliband and have a sneaking suspicion he may return strengthened by his time out in the real world. But this lot? The Chuka Harman Burnham Hunt Balls brigade? I can't, in all seriousness, go into a booth and put my mark on any one of them,” she wrote.Reuse content