Solicitors representing the families of ten of the 21 people killed in the 1974 Birmingham pub bombings say they are disappointed by the coroner's decision to appeal the inquest judgment.
Last Friday, a judicial review recommended that the coroner include the question of who had planted the bombs, an issue which families of victims had sought to be included.
Sir Peter Thornton QC, who is overseeing the new inquests, had previously said he would not include in his inquiry the issue of who planted the bombs as it fell outside the scope of an inquest.
That decision dismayed the families of some of the victims and they brought a judicial review of his decision.
Last week a court ruled in the families' favour, but it was not mandatory.
In statement today, the coroner said he feels the legal issues raised by last week's ruling require reconsideration and clarification and he will appeal the decision.
Mr Thornton said he had considered carefully last week's judgment on the scope of the inquests saying it was a complex matter relating to "the purpose of an inquest and the approach of a coroner to setting the boundaries of his or her investigation".
The questions raised by the judgment are "vital to the inquest ... and also of general public importance," he said.
As a result a pre-inquest hearing which was due to take place on 22 February has now postponed.
The families involved say they now intend to apply for legal aid funding to help them in the appeal process.
They were previously turned down for financial help by the aid agency and instead raised funds to help the legal process through a public appeal.
Christopher Stanley of KRW Law said there had always been the possibility that the coroner would seek to appeal last week's decision.
Mr Stanley said there were important points of law in the matter, and that there will be continuing struggles regarding funding for their clients as a result of this further legal development.
This, he added, should not be another burden for the families involved.