CVs from six fictitious candidates - who were given "white", black African or Muslim names - to 50 employers in the BBC Radio Five Live survey.
White candidates were much more likely to be given an interview than similarly qualified black or Asian people.
TUC boss Brendan Barber called for new laws in the face of "shocking" results.
The employers targeted by the undercover survey were selected at random from newspaper adverts and recruitment websites.
Many of the firms were well known and the jobs covered a range of fields, Radio Five Live said.
All the applicants were given the same standard of qualifications and experience but their CVs were presented differently.
Almost a quarter of applications by two candidates given traditionally "white" names - Jenny Hughes and John Andrews - resulted in interview offers.
But only 9% of the "Muslim" applications, by Fatima Khan and Nasser Hanif, prompted a similar response.
'Treated unfairly'
Letters from the "black" candidates, Abu Olasemi and Yinka Olatunde, had a 13% success rate.
Mr Barber, general secretary of the TUC union, suggested private firms should have to follow the same anti-discrimination guidelines as the public sector.
He said: "Statistics as shocking as these suggest that many people recruiting for the private sector firms are harbouring inherently racist views.
"Public sector bodies have to prove there are doing all they can to eliminate race discrimination.
"Until the Race Relations (Amendment) Act is extended to the private sector, black and Asian people will continue to be treated unfairly and will be denied the opportunity to succeed at work."
Professor Muhammad Anwar, of Warwick University's centre for research in ethnic relations, said the survey was proof of a recent rise in anti-Muslim feeling.
He said: "I think there is a trend now or a shift from racial discrimination to more religious or cultural type discrimination.
"Certainly after 9/11 there has been a tremendous difference.
"When people look at Muslim men they may think again about whether that person should be invited for interview."
The radio producer who carried out the survey said he had been "surprised by the sheer extent" of religious and racial discrimination it uncovered.
