The company came 23rd in an official league table of 24 insurance companies berated for dragging their feet over settling claims.
Colonial has settled 32 out of 6,754 cases, and Hogg Robinson has settled just one case out of 602.
Despite Colonial's public shaming, NASUWT general secretary Nigel de Gruchy said the union would not sever its links with the company.
He pointed out that the total number of Colonial cases needing review was much smaller than the 58,606 cases involving the Prudential, which runs the teachers' additional voluntary contributions scheme .
TES2, page 23