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Douglas Alexander, the Labour Party's election coordinator says he expects the Conservatives to outspend Labour "by as much as three to one".

The Tories are expected to run a £19.5 million election campaign - that's the legal maximum that can be spent in the year running up to an election - according to the Times.

“We can’t match their kind of spending," a senior Labour figure told the Times, "We do not have two dozen people in the City in hedge funds who can give us huge amounts of money."

Indeed, in the first three quarters of 2014 the Conservatives received 34% more in donations than the Labour Party, according to figures obtained by the Electoral Commission.

So who writes the cheques for David Cameron's party?

Here are the five biggest donors from January to 30 September this year.

1. A multimillionaire climate change skeptic - £1.5m

British-Australian businessman Michael Hintze runs the £5bn hedge fund CQS. He is also a former Australian army captain. He funds organisations that cast doubt on the science and cost of tackling climate change, such as Lord Lawson's Global Warming Policy Foundation.

2. A city financier - £893,979

Conservative Party chairman Michael Farmer has donated almost £7m since 2001. This summer he was made a peer by the Tories, sparking a cash-for-honours row. He also runs the hedge fund Red Kite Capital Management.

3. A multimillionaire banker - £772,936

James Lupton was a director at Barings, the bank which collapsed in 1995. He then co-founded Greenhill Investment Bank and was awarded a CBE in 2012. He is the Conservative Party's co-treasurer.

4. A multinational corporation - £713,180

JC Bamford (also known as JCB) is the world's third-largest construction equipment maker. Over the last decade the Bamford family have donated at least £5m to the Tory Party.

Since David Cameron became Prime Minister, company chairman Sir Anthony Bamford has been a regular guest on the PM's trade missions abroad. The Prime Minister's seminal immigration speech was held at JCB’s Staffordshire factory in November last year.

A first attempt to install Sir Anthony in the House of Lords was blocked because of concerns over his tax affairs. Sir Anthony eventually took a seat in the Lords in October 2013.

5. The Addison Lee tycoon - £500,000

After John Griffin - founder of minicab firm Addison Lee - donated half a million pounds to Tories earlier in the year, annual checks on taxi licence holders were replaced with reviews every three years. Some believe John Griffin used his wallet to influence the legislation, after lobbying for the deregulation of taxi firms.

[Source: Electoral Commission, Times, Guardian]