Party primaries, such as the one held recently by the Tories in Totnes, are a sham.
The candidate is elected from a closed list drawn up by the party leadership either locally or increasing nationally; these sorts of closed-list elections resemble those formally held in Eastern European. Such primaries give the appearance of choice to local electors, but the actual amount of real choice, if any, in terms of candidates’ policies is determined by the party leadership which drew up the list.
Moreover once the candidate is elected he or she is then bound by a centrally determined manifesto, and, if elected, is subject to the party whip in parliament.
Primaries also finally render local party activists utterly powerless. Joining a party will give them no say in candidate selection at all, so there is little incentive to become active in local politics. The main beneficiaries of primaries are not the local electors, nor the rank and file party members, but top brass of the party itself.
It is precisely these anti-democratic features which make primaries attractive to New Labour politicians such as David Miliband. At a stroke they see how they can rid themselves of any residual trade union and local activist pressure.
Proportional representation (under any of the PR systems) plus the devolution of power to local councils would actually increase the amount of democracy. Yet both Cameron and Miliband run a mile from such proposals.