Lisbon accent is definitely not a neutral one! While in Porto people use ‘b’ instead of ‘v’, in Lisbon people use ‘v’ instead of ‘b’... and this is just a small example.

And another thing is… there is no neutral accent. There are different accents and that’s it! People in Porto speak one way, in Bragança they speak in another way, in Faro another and so on…

You have to admit that this fact is what makes our language so rich. :P