Urdu should be official along with English and the Prime Minister or any other individual representing Pakistan on an official level should use either of these two languages. Whilst I agree that knowledge of English can be a plus point when interacting with other nations it is also nevertheless important to realize that not all of our official representatives are especially competant in the English language. Rather than making a joke out of ourselves hence it is better if that individual opts for Urdu. After all in this day and age practically all country's except the post colonial nations of Africa and some in Asia use their own languages on an official level rather than the language of their former colonial masters (S. America is a slightly different case as like the US a large chunk of the population there are actually European descendents and Spanish culture and language as such arent alien to South American countries in the way that French is for the Ivory Coast or English for Pakistan). If China, Malaysia, India and even Yemen can speak on international forums in their own languages then I see no reason why Pakistanis should be under any complex that speaking our own language will make our presence less valuable there. But as said if an individual representing Pakistan is competant in English then he should opt for that language as it breaks linguistic barriers.