Tomdg in the comments suggested that the proposal of the POWER report supported by Johann Hari would be a good way to reform party funding.
Mr Hari writes:
The real solution was laid out in Helena Kennedy’s brilliant Power Commission a few weeks ago. She suggested that each voter should be asked to nominate a political party to receive three pounds of public funds a year. The political parties would – in a swoop – become more accountable to us, not to Chai Patel.
I'm going to assume that the tick box for your vote and your cash are separate, and it is possible to abstain from nominating any party even if you don't want to abstain from voting. Without those two caveats it is worthless because of the need for tactical voting under a First Past the Post system. With them it does have some merit.
However it also has problems, such it is centralising. The money goes from taxpayers to the treasury, then to central offices, and only then is feed back out again. Or not, depending on whether central office decides that that particular candidate is worthy it's largess. Don't do what central office thinks is right and suddenly your seat might no longer be a priority.
As
Daniel Finkelstein pointed out in The Times
the state funding of political parties will make it still worse, certainly in the form that is being considered. The State will bestow its financial favours on central party organisations. Private fundraising will be severely restricted. Discipline will be rewarded, the maverick punished, and independence of view militated against.
And it is independence of view that is important in politics, not robots following the party line.
Without a plurality of views opinions all you get is an echo chamber with everybody reinforcing each others mistakes. The best ideas can never be found if it is not even put forward for debate.
John Stuart Mill shows up the shear arrogance implicit in this stifling of opinion in favour of the party line
if any opinion is compelled to silence, that opinion may, for aught we can certainly know, be true. To deny this is to assume our own infallibility.
Cameron and Blair might consider themselves infallible, but experience shows that they, and every other political leader, certainly are not. This is the whole point of a Parliament, to have representatives of a multitude of differing opinions, debate them, and through the debate discover the best. By centralising funding through the party hierarchy you snuff out that debate before it can begin.
The reply to this will be: But even if it makes the individual MPs more subservient to their parties it will make the parties more responsive to the people, as they are not just voting them power but voting the cash to campaign. Unfortunately this isn't strictly true.
The standard deviation of percent of the vote for all 3 main parties over the last 50 years is roughly 6%. That is in any election the parties can expect that their share of the vote is going to go up or down by 6% per election, which under the power proposals would mean that their funding would also on average change by about only 6% per election either way.
Or to put it another way; even if they do as badly they are going to see about 90% the maximum funding they could expect come rolling in no matter what. Not a great incentive to be responsive and go that extra mile for their voters.
I have already linked to
examples as to why, despite the damage outlined above, state funding of political parties will not even solve the problem of party corruption, and could make it worse.