This summer will be remembered for Labour's final betrayal of the working-class people it was founded to represent. Not content with signing up to Conservative austerity measures that are dragging Britain's most vulnerable people deeper into poverty, Ed Miliband has turned his back on the union members who supported his leadership bid.

Austerity has not fixed the economy, while the poor pay the social cost. Labour has failed to make the argument that it was not welfare spending that wrecked the British economy, but a crisis of unfettered capitalism. Miliband cannot even promise to reverse the brutally unfair bedroom tax, which has already claimed its first life with Stephanie Bottrill (Comment, 31 May).

We urgently need a new party of the left. Labour will not provide the opposition to coalition policies that the situation demands. We need to provide a genuine alternative to the austerity policies which the three main parties support. A party that is socialist, environmentalist, feminist and opposed to all forms of discrimination.

Since we launched our appeal in March to discuss founding such a party, more than 9,000 people have signed up and more than 100 local groups have been established across the country. As Left Unity moves towards its founding conference on 30 November at the Royal National hotel in London, we call on all those who are sick of austerity and war, who want to defend the NHS and our public services, and want to see a fairer Britain, to join us.

Gilbert Achcar, Jean Alain Roussel, Alan Gibbons, Zita Holbourne, Kate Hudson, Roger Lloyd Pack, Ken Loach, China Miéville, Michael Rosen

www.leftunity.org/appeal