She says Labour is allowing Fine Gael to pursue endless austerity policies which go against the party’s core values.
“The policy of austerity is discredited in Europe and, increasingly, at home,” she wrote, saying those policies are a “profoundly immoral way to run our country”.
Ms Childers said she had increasingly found herself discouraged and prevented from advocating a distinctive social democratic position within the Labour party.
“While I have remained constant in my views, the Labour leadership has drifted away from a progressive policy approach,” she wrote.
“My attitude is vilified as disloyal or opportunistic when, in fact, I am defending and promoting the party’s core values.”
The MEP for Leinster resigned from the Labour Parliamentary Party in April.