Ed Miliband has put pressure on Premier League football clubs to follow the example of Chelsea and Hearts and pay all their staff a living wage.
The Labour leader said that many football clubs are lined up alongside law and accountancy firms as workplaces where star performers earn seven-figure salaries while security guards, cleaners and caterers "struggle to make ends meet".
Calling for a "reality check about inequality in Britain", Mr Miliband said the Government should do more to work with employers to pay the living wage of £7.65 an hour or £9.15 an hour in London.
"Firms that can afford to pay multi-million pound salaries at the top need to explain why they will not pay the Living Wage to those at the bottom," he said in a post on Facebook.
Chelsea last month became the first Premier League club to commit itself to pay the living wage, while Edinburgh club Heart of Midlothian became the first Scottish side to do the same in October.
Mr Miliband, who has committed Labour to increasing the national minimum wage from its current £6.50 an hour to £8 by 2020, warned of a "strange disconnect" which has seen rewards at the top of companies soar while average pay packets fall in real terms.
The number of people earning below the living wage has risen from 3.4 million to 5.3 million since the 2010 general election, while FTSE 100 directors saw their rewards increase by 21% last year alone, he said, citing statistics suggesting chief executives at the biggest firms now earn 130 times more than their average employee and 300 times the living wage.
"I know there are many brilliant executives in this country who deserve to be well-rewarded, but there is a strange disconnect in the debate today," said the Labour leader.
"For example, this weekend, many people will be going to football matches where the stars are paid six figure sums every week, but those who work at the stadium are often paid significantly less than the living wage. There are some clubs, like Chelsea in London and Hearts in Edinburgh that have become accredited living wage employers. However many other football clubs - including some of the giants of the Premier League - have not."
Mr Miliband said that most big banks now pay the living wage to their lowest-paid workers, and have reaped benefits in "higher productivity, staff retention and morale".
But he said: "More needs to be done in sectors like law and accountancy which are estimated to have more than 1,000 employees paid upwards of £1 million a year - but cleaners, security guards and caterers who take care of them at work often struggle to make ends meet at home."
Labour has promised tax rebates for employers which sign up to the living wage within a year of the May election, as well as putting employee representatives on remuneration committees and requiring companies to publish the ratio between their highest-earners' pay and the average member of staff.
Mr Miliband's comments came as former Cabinet minister Peter Hain called for more borrowing to pay for £30 billion a year of investment in housing and infrastructure if Labour wins the election.
Mr Hain, who is standing down from Parliament at the election, also proposed the abolition of the upper earnings limit which sees National Insurance paid at a rate of 2% on income above £805 a week, compared to 12% below this level.
Abolishing the upper earnings limit could raise £8 billion a year from high-earners to help fund the NHS and elderly care, he said. Coupled with Labour's plan to raise the top rate of income tax from 45p to 50p, it would increase the combined top rate of income tax and national insurance paid by the richest in society from the current 47% to 62%.
Setting out his proposals in a book entitled Back to the Future of Socialism, Mr Hain asked: "Why should people on high earnings pay standard rate national insurance contributions on only part of their earnings when lower-paid people must pay contributions on all their earnings?
"Scrapping the reduced rate may make it possible to lower the standard rate so that only people on very high earnings pay more, or to raise the lower earnings limit at which people start to pay national insurance contributions, to help the low-paid."
Mr Hain added: "Higher government borrowing today can mean lower borrowing tomorrow by getting the economy growing again and keeping the engine of growth in gear. There is a better alternative to Tory cuts. That is for Labour to cut government borrowing more slowly, take longer to bring debt down, and allow faster economic growth to bear more of the burden of deficit reduction."