Attorney General Trstenjak has given his opinion in the Lassal case (referred to the ECJ by the Court of Appeal) and has concluded that five years of residence under previous Directives does impart a right of permanent residence under the Citizens Directive (Directive 2004/38/EC).
See paragraphs 81 to 93 and this conclusion at paragraph 93:
‘In conclusion, it must be stated that, irrespective of the meaning finally to be given to the second sentence of recital 17 in the preamble to the directive, it is in my opinion clear at least that it does not justify the conclusion that only a period of residence completed in accordance with the national provisions enacted in order to transpose Directive 2004/38 and applicable from 30 April 2006 can qualify as a period of legal residence within the meaning of Article 16(1) of the directive. On the contrary, a period of residence completed in accordance with the predecessor provisions of Directive 2004/38 is also a period of legal residence under Article 16(1) of the directive. The objection based on the concept of legal residence put forward by the Government of the United Kingdom and the Belgian Government is therefore not convincing.’
This is the opposite conclusion to that reached by the Asylum and Immigration Tribunal in other cases, such as OP (EEA; permanent right of residence) Colombia  UKAIT 00074. The AIT did in its day seem to have a tendency almost always to err in law on the side of caution, otherwise known as the side of the Home Office.
The facts of Lassal were that a French national who resided in the UK between September 1999 and February 2005. She left the UK for 10 months and after she returned she was refused income support on the basis she had no right of residence. The Child Poverty Action Group intervened in the case.
An opinion of an Attorney General is not the same as a judgment of the ECJ, but the ECJ will usually follow the same approach as the AG. This is therefore a strong indication that the ECJ will hold that residence under previous directives can contribute to or give rise to the right of permanent residence under the Citizen’s Directive.