The family and colleagues of murdered Belfast solicitor Pat Finucane today warned the British government they will use all legal and political means at their disposal to secure a satisfactory inquiry into his murder.
Mr Finucane's widow Geraldine and her solicitor Peter Madden claimed the British government may have breached an international agreement with the Republic by setting up an inquiry under the new legislation.
They also revealed the family is seeking meetings with the Ulster Unionists and Rev Ian Paisley's Democratic Unionists and also hoping to brief key American politicians when Mrs Finucane travels to the United States next week.
Mr Madden said: "The problem we have with an inquiry set up under the Inquiries Act is that it gives the Government power to take decisions which the tribunal itself cannot overturn.
"The decision-making process has been taken away from inquiry judges to the Government and in a case like Pat's where the state's role in a murder is under examination that takes away any independence an inquiry may have.
"The setting up of the inquiry under the new legislation also breaks an international agreement with the government which committed the British Government to setting up the inquiry under the terms of the 1921 Inquiries Act.
"We have the support of the Irish Government in our campaign and we believe we have US Government support.
"The family are determined this will not rest and they will not accept second best."
Pat Finucane was gunned down in front of his family in his north Belfast home by the Ulster Freedom Fighters in February 1989.
Last year, loyalist Ken Barrett was jailed for 22 years after admitting his role in the shooting. However, the murder has been dogged by allegations that members of the security forces were involved.