Public standards chief says Cruddas incident is just the latest breach of ethics in UK political lobbying
The "cash for access" row involving Conservative party co-treasurer Peter Cruddas has thrown a spotlight on the debate over political funding, which has been prompted by allegations of donors trying to buy influence.
David Cameron denounced lobbying – an industry estimated to be worth £2bn – as "the next big scandal waiting to happen" in a speech in February 2010.
Pledging to "shine a light of transparency on lobbying", the prime minister warned that it tainted politics, crossed party lines, and went "to the heart of why people are so fed up with politics".
Yet five years since cross-party talks began on changing the system, with state funding for parties and donation caps all on the table, no consensus between the three main parties has been reached.
Danny Alexander, the chief secretary to the Treasury, said talks on reform would start shortly, with a "short, sharp series of discussions over the next few weeks under Nick Clegg's leadership".
Meanwhile, the chairman of the independent committee on standards in public life, Sir Christopher Kelly, warned: "It would be wrong to regard [the Cruddas allegations] as an isolated event. Events like it are inevitable as long as the main political parties are dependent for their existence on large donations from rich individuals or, in the case of the Labour party, a small number of trade unions."
The Cruddas allegations are the latest in a series over cash for access and influence made against both the Conservatives and Labour in recent years.
The last two years of Tony Blair's tenure at No 10 were dogged by allegations of links between the granting of honours and financial support for parties.
The "cash for honours" affair centred on claims that millionaires who gave large loans to Labour were to be given peerages. It was claimed several had loaned large amounts of money to Labour at the suggestion of Labour fundraiser Lord Levy.
A police inquiry followed a complaint by Scottish National party MP Angus MacNeil that financial support was being rewarded with honours, in contravention of a 1925 anti-corruption law.
Blair became the first prime minister to be interviewed by police, though not under caution, as part of a political corruption inquiry. Levy and Blair's former adviser Ruth Turner were arrested and questioned. They denied any allegation of wrongdoing.
After a £1.4m, 19-month investigation, the Crown Prosecution Service announced that nobody would be charged, as there was no realistic prospect of a conviction.
An influential group of MPs which considered the issue said in December 2007 that membership of the House of Lords should be decided by an independent body in a fully transparent process.
The then chairman of the Public Administration Committee, Dr Tony Wright, said that though no charges were brought over the allegations, trust in public life had been damaged.
Other incidents of alleged financial irregularity by politicians include the notable "cash for questions" affair, when, following a Guardian investigation, MP Neil Hamilton was accused, along with fellow Conservative Tim Smith, of taking cash in brown envelopes from Mohamed Al Fayed, the former Harrods owner, to ask questions in the House of Commons.
Smith admitted to the payments and resigned immediately. Hamilton, who was forced to resign as corporate affairs minister, protested his innocence.
In 2009, two Labour peers, Lord Truscott, a former energy minister, and Lord Taylor of Blackburn, were found by a Lords committee to be willing to change the law in exchange for cash following a sting known as "cash for amendments" by two Sunday Times undercover reporters. Both were suspended from the Lords, the first peers since 1642 to be punished in this way. Both denied wrongdoing.
Two years ago, there were also allegations over so-called "cash for influence" when three former Ccabinet ministers were suspended from the Parliamentary Labour Party over claims they were prepared to influence government policy for payments. Geoff Hoon, Stephen Byers and Patricia Hewitt were filmed by Channel 4's Dispatches programme discussing the possibility of working for what they thought was a US lobby firm.