Praveen Halappanavar has also had offers of support for his case from lawyers, doctors and human rights groups "from around the globe".
"We are already working on the next legal step which is taking the case to Europe," said Mr O'Donnell, "and we will ask the courts to rule against the Government on its refusal to hold a public inquiry into Savita's death."
Mrs Halappanavar, a 31-year-old dentist, died at Galway University Hospital on October 28, a week after being admitted.
Mr Halappanavar claims he and his wife, who was miscarrying their child, made requests for the termination of the pregnancy but this was refused.
He claims one medic said the operation wasn’t possible because this is “a Catholic country".
Mr O'Donnell said: "We have asked for a response by Friday lunchtime but we don't expect one so we are already moving ahead with taking the case to the European Court of Human Rights. Praveen is determined that the two inquiries being held by the HSE and HIQA fail him as the next of kin."