With the 2015 election date rushing towards it, and having seriously ticked off some of its big union donors, the Labour party is desperate to find pots of cash to match the Tories' traditionally blue-chip campaign funding. But where is this secret Santa Ed Miliband is seeking?

Talk of persuading armies of individual union members to pitch in with their pound coins, or even five pound notes, remain an unfulfilled fantasy. So – and this has the ring of familiarity about it – up step the big hitters.

Luckily for Miliband, they don't come much bigger than his best pal and not-so Secret Santa, the property developer Andrew Rosenfeld, one of the country's richest men with an estimated wealth of £100m, who is ready to write a cheque for £1m or more to the party and encourage others to do the same.

The first time many heard of Rosenfeld was when he was caught up in the "cash for honours" affair in 2005, in which wealthy businessmen were accused of making big, secret loans to Labour in return for honours, including Peerages.

The extraordinary episode even saw prime minister Tony Blair interviewed by the police in 10 Downing Street. But, in the end, no charges were brought against anyone allegedly involved. And Rosenfeld was never accused of any wrongdoing.

He had previously lent £1m to Blair's Labour party, which was paid back in 2009, but he reportedly donated another £1m after the election with promises of more to come. That will make him the biggest individual Labour donor, beating Harry Potter author JK Rowling.

And that does not include extra cash from his "ethical" phone company The People's Operator which donates to charities and has a partnership with Labour.

Miliband has appointed the 51-year-old Rosenfeld as his "chair of nations and regions" with the job of boosting local supporter engagement and raising funds. It is also believed he will have a significant role in the party's election war room.

The businessman's prime objective will be to help the party secure key marginal seats but also come up with ways of engaging local supporters and boosting donations through Labour's Thousand Club, which requires members to pledge at least £100 per month to the party, and elsewhere.

But their relationship goes beyond a purely political or business one.

Rosenfeld's current partner, Juliet Soskice, is reportedly one of Miliband's first girlfriends and is close to him and his wife Justine. They socialise regularly, most recently along with other senior Labour figures at Rosenfeld's Christmas party at his Regent's Park home, not a million miles away from Miliband's north London home in Dartmouth Park, Camden.

Labour MPs and others are also said to have visited him during the summer at a villa he rented in Tuscany.

Rosenfeld made his money through property development but has always been engaged with, and contributed hugely to charitable causes.

Until 2005 he was chairman of the property firm Minerva which he co-founded with an issued share capital of £70,200 and which was worth an estimated £600m when he stepped down.

And for five years he was based in Geneva, where he set up the property investment group Air Capital, although he denied claims he was a tax exile, insisting he chose Switzerland for "lifestyle reasons" and paid taxes there.

However, last year prime minister David Cameron reacted to Labour attacks on the Tories' big donor Lord Ashcroft's tax exile status by suggesting Ed Miliband examined Rosenfeld's own record and background.

Until 2007 Rosenfeld was head of the UK National Society for the Prevention of Cruelty to Children's FULL STOP campaign, raising £250 million which is the largest sum ever raised in Britain for a single children's appeal.

He has served as the UK Chairman of Fundraising and Appeals for UNICEF and until June 2006 was a trustee of the major charity Jewish Care.

He was listed at number 700 on the Sunday Times Rich List 2007 but moved up to number 540 in 2009.

In 2012 Rosenfeld founded a new "ethical" mobile phone company TPO (The People's Operator) that contributes 10% of income and 25% of profits to charity and other non-profit organisations.

It's mission statement is "to raise millions for good causes" and it works in partnership with charities including Childline, the NSPCC and the Big Issue.

It also declares it is "proud to be working in partnership with progressive causes that champion social issues and fight to change lives for the better" and lists the Labour Party and the GMB and Unite unions as partners.

The company reportedly gave free calls to Unite strike committee members when they were carrying out a campaign during the controversial Grangemouth oil refinery dispute earlier this year.

Rosenfeld's support and friendship is clearly a big plus for Miliband as he attempts to re-shape his relationship with the traditional financial backers in the union movement.

And there seems little doubt he will need more large individual donors, which Rosenfeld is expected to help woo.

But there are concerns in the wider Labour party over the danger of the big union funders being replaced by big, wealthy individual donors. Something Blair was accused of promoting and which led the last government into some serious troubles even in it's early days with the Bernie Ecclestone affair.

That saw the Formula 1 racing boss donate £1m to the party at a time he was trying to persuade the government to ditch its pledge to ban tobacco sponsorship of the support, which he succeeded in doing. Blair had to apologise, famously stating he was a "pretty straight kind of guy" and repay the cash. Then there was the whole cash for honours crisis.

There is no suggestion that Rosenfeld is anything other than a genuine supporter with no other agenda. But that has not stopped some in the party worrying about the close relationship between their leaders and big money.