It's not actually true that Parliamentary Private Secretaries are not allowed to sign Early Day Motions. In fact even gvernment Ministers can sign them.

They always say they aren't allowed, and they may even believe it, but if they do believe it, it just means they have not done their homework. This site explains about all that stuff.

I think John Tiffney's remark here is actually very useful. If he actually said it, and was speaking on behalf of the LGA, that in itself will serve to discredit anything else the organisation says, sinc eit is such an idiotiuc thing to say. It deserves to be publicised as widely as possible. It has the handy quality of being recognisably an insult to the whole country.