FORMER prime minister Datuk Seri Mohd Najib Razak (picture) and his son Datuk Mohd Nazifuddin have failed to get constitutional issues referred to the Federal Court relating to his RM1.69 billion tax arrears appeal.The Court of Appeal has dismissed an application by lawyer Tan Sri Muhammad Shafee Abdullah, who represented for Najib and Mohd Nazifuddin, to refer constitutional issues involving Section 106 (3) of the Income Tax Act 1967 to the Federal Court.