Liberal Democrats cheekily tried to highlight Labour's internal battle over Progress today, when they invited the group to their party conference.
Unions have been trying to have the New Labour organisation expelled because of its private funding model - much to the anger of centrist MPs in the opposition party.
"I have noted the moves from the GMB [trade union] and others within the Labour party to sideline Progress and force its members out of the party," Lib Dem president Tim Farron wrote in a letter to Progress chairman Andrew Adonis today.
"This is a great shame. I do not mean to patronise you or your members by suggesting your response should be to join the Liberal Democrats.
"I know that you very much consider yourselves a part of the Labour movement. But you are modern, progressive reformers and you deserve to be a part of the political debate in this country."
The letter then proceeds to invite Progress to the party's autumn conference, because the Lib Dems "are a party that is prepared to work with others for the good of the country".