Why should parties be funded by the state?

If political parties are not funded, they would then be funded by wealthy individuals which is not fair.
Rise of large individual donations to PP’s since the 1990s has led to the perception that one might be able to buy access or political influence.
g., in 2006 there was the so called ‘Cash for honours scandal’, whereby PM TB appointed a sig. no. of Life Peers to the House of Lords – it was alleged that the individuals were appointed because they’d made sizeable loans to the party.
This shows that political parties should be funded by the state because it shows that often individual donations made to parties are only done in order for people to gain influence or a position of slight power.
Also, in 1997, Bernie Ecclestone donated £1 million to the Labour party, which many felt had prompted the delay in the introduction of the ban on tobacco advertising in Formula 1 moto racing, thus he bought influence.

State funded political parties would give 3rd parties a more equal footing
In the first quarter of 2016, The Liberal Democrats received 79 donation, whereas the Labour party received 150 and the Conservative Party received 269 donations.
This shows that individual donations give the 2 main parties an unfair advantage over smaller, minor parties which means that they can’t perform as well.
Funding would likely be based entirely on membership or electoral performance, meaning that it would be more equal, as third parties might have a very large membership so the SNP for example, in 2016 had 120,000 members whereas the Conservative party also had around 120,000 members → h/e conservative party received much more funding, so if it was based on membership performance it would be much more equal.
2015 Sunday Times Political Rich list featured the top 197 donors to pp’s – 151/197 donated to the Tories → unfair to other parties, especially 3rd parties and so state funding would reduce this disproportion

State funding would allow politicians to focus on representing their constituents rather than courting potential donors.
Parties such as the Liberal Democrats could compete on an equal financial footing because funding would be based entirely on membership or electoral performance.
Also, not that drastic – 50p per voter per year and already exists in Commons (Short Money) and Lords (Cranborne Money).
Funding would allow smaller parties to compete effectively on a national scale and therefore reduce dominance of main two parties.

There have been attempts by parties to circumvent the PPERA’s regulation of donations by encouraging supporters to offer the party long-term, low interest ‘loans’. It was this tactic, and the inducements supposedly offered to secure such lines of credit, that gave rise to the ‘loans for peerages’ scandal during Labour’s time in office (1997-2010).
Although the police investigation into that scandal ultimately ended without any prosecutions being brought, the issue of party funding is still controversial, as seen in the efforts to address the status of donors not registered as UK taxpayers under the PPEA.
In 2015, when the Labour Party’s membership enjoyed an unprecedented upsurge, membership fees only accounted for 19% of the party’s overall annual income.