Heidi Allen has revealed she would never let Tony Blair join Change UK because he is too "tarnished".
The Change UK leader made the comments during a 'Beer and Brexit' Q&A event at London's Bush House.
"The worst part, as I have discovered getting into politics, is once you are tarnished, you are tarnished," Ms Allen said.
"It is unforgiveable and very different to any other kinds of work, but the fact is you are."
She continued: "And for all the great stuff people might think of him [Tony Blair], 'He has been responsible for the Iraq war' hangs around I'm afraid."
In February, a talkRADIO poll revealed that just seven per cent of respondents would like to see Tony Blair return to politics with a role in Change UK - then known as the Independent Group.
Of the 3,300 people asked in the week-long poll, an overwhelming 93 per cent said they would not like to see the former Prime Minister return to frontline politics.
Heidi Allen recently hit out at Brexit Party leader Nigel Farage, calling him a "coward" for refusing to take part in a live TV debate with her ahead of the EU elections.
Ms Allen later tweeted: "Breathtaking arrogance from Farage - if he seriously believes that the British people aren't entitled to hear his vision for the country compared with others, then he doesn't deserve to represent them."