Lord Browne of Madingley, the former chief executive of BP, has said that homophobia is still commonplace in public life.
The 62-year-old was forced to resign in 2007 after lying in court papers how he had met his boyfriend, who had outed him by selling his story to a newspaper.
Writing for the Guardian, Lord Browne said gay men and lesbians still feel they have to hide their sexual orientation to succeed.
He cited the case of David Laws, the Liberal Democrat MP and former Chief Secretary to the Treasury, who resigned after allegations he wrongly paid expenses to his male partner.
Mr Laws said he was trying to keep his relationship with lobbyist James Lundie secret.
Lord Browne wrote: “The recent resignation of David Laws… suggests that public figures continue to feel they have no choice but to cover up their sexuality.
“Let’s be clear: if he [Laws] was indeed concealing the fact that he was claiming money for a partner, then he was doing something wrong.
“But it is a great shame that a public figure, a generation younger than me, still feels the need to hide his sexuality.”
Lord Browne singled out the business world and sport as spheres where intolerance remain.
He continued: “I suspect that the sad story of David Laws will not be the last.
“Despite the exemplary diversity policies in many companies, my sense is that the business world remains more intolerant of open homosexuality than other walks of life such as the professions, the media and the arts. And it is extraordinary how few openly gay sports stars there are.
“Even in today’s more tolerant age, there are many lonely people out there still afraid to reveal who they really are for fear of marginalisation and abuse. It can only be a matter of time before someone else finds themselves ‘outed’ on the front page of a national newspaper.”
Lord Browne was outed when his former lover, Jeff Chevalier, went to a newspaper with relevations about their relationship.
While trying to prevent the kiss-and-tell story from being published, the peer said in written court submissions that they met in Battersea Park. However, they met through an escort agency.
He said he believed it helps to see other gay people coming out in prominent public roles, as this “multiplies” the positive impact of making the decision.
Yesterday, former business secretary Peter Mandelson said he was proud of having demonstrated that people can reach the top regardless of whether they are gay or straight.
Lord Mandelson, who was the de facto deputy prime minister and most powerful gay man in the country during the last Labour government, has kept his private life closely guarded for decades.
But he told the Times: “I think I’m actually quite a good role model for people who, without any fuss or bother, without any self-consciousness or inverse or other discrimination, [are] able to make it in politics, to make it in public life, to make it to the top places in government of our country.”