The Daily Express owner Richard Desmond has donated £1m to UKIP's election fighting fund, bringing his total contribution to £1.3m.
It was hailed by UKIP leader Nigel Farage who said that he hoped other wealthy backers would now follow his example.
Desmond, who donated £300,000 to the party last year, said he believed the party would "stand up for people who are struggling".
The news was reported on the front pages of both the Daily Express and Daily Star today (above). Desmond also owns the Sunday Express and Daily Star Sunday.
"I firmly believe in UKIP. It's a party for good, ordinary British people. It is not run by elitists," Desmond was quoted as saying in the Daily Express.
"They are struggling to have a voice. They do not have a massive party machine or highly paid public relations people.
"They are human; they are not perfect and they do not pretend to be. But what they believe in is the best for the British people. They are the sort of people who will stand up for people who are struggling."
Farage said: "Richard Desmond is a self-made man, who has done a brave thing in coming out for UKIP today. I hope that many others will now follow suit."
A Daily Express editorial on Wednesday described UKIP as a party "that speaks for a large number of ordinary Britons".
It said: "While there is no realistic chance of Nigel Farage walking into Number 10 on May 8 it is still reassuring to supporters that his party exists to fight on such issues. After all, pressure from them has already helped to convince the Conservatives to adopt Ukip-friendly policies, notably David Cameron's promise of a referendum in 2017.
"However many seats Ukip wins in the General Election, it is a powerful advocate for causes that large swathes of the British public believe in."
National Union of Journalists general secretary Michelle Stanistreet said: "It’s a complete outrage that Richard Desmond has delved deep in his pocket and handed over a £1million bung to UKIP, yet for the seventh year running has denied his workforce a pay rise. That’s on top of the £300,000 he handed over to Nigel Farage last year.
"In his statement Desmond says he backs UKIP because they stand up for people who are ‘struggling'. What about his own staff who have been struggling without a cost of living increase for years? His justification for this in his statement today would be laughable if it wasn’t so sick-making.
"Desmond has used Express Newspapers as a cash cow for years, starving the titles of the resources needed to produce decent newspapers, all the while treating staff with contempt. Now, before he moves to sell the papers he’s long tired of, he’s trying to use the influence they bring to persuade anyone fool enough to indulge him that he’s due a peerage. Today we see him trying to dress up his pathetic desire for a gong and ermine robes as a blow to the establishment on behalf of the common man. It seems in Nigel Farage and UKIP, he’s struck upon natural bedfellows.
"This latest tawdry episode epitomises all that is wrong with the ownership of British newspapers, a system that allows tax avoiders and asset strippers to diminish and degrade once respected national titles. That’s why his own staff have had enough and why the NUJ wants these newspapers to be sold to someone who cares about journalism, and who is prepared to give this business a future."
A union spokesman for Express Newspapers journalists said: "We are astonished that Nigel Farage has allied himself with a man who has become the unacceptable face of British business in the 21st century. Richard Desmond is a billionaire who enjoyed a £360 million windfall from the sale of Channel 5 last year and saw his Northern & Shell company record a £37 million operating profit. Yet for the seventh consecutive year, he has refused to give his employees a pay rise.
"Is that what UKIP stands for? A billionaire who has made his workforce 20 per cent poorer in real terms since 2008 by refusing to give them a pay increase?
"Mr Desmond, Britain's greediest billionaire, has insisted he cannot afford to give us a pay rise because it would cost Express Newspapers £800,000 but he can afford to give at least £1 million to Mr Farage. This is an insult to hardworking people. We believe that this donation is linked to the Conservatives' refusal to give Richard Desmond a peerage. In our view, giving him a peerage would bring the honours system into serious disrepute."
Email email@example.com to point out mistakes, provide story tips or send in a letter for publication on our "Letters Page" blog