Detectives are looking into allegations that a second newspaper at Rupert Murdoch's News International may have used hacked voicemails to publish stories about the private life of a prominent public figure.

Andy Gilchrist, a former union leader, has asked Scotland Yard to investigate his belief that interception of his mobile phone messages led to negative stories about him appearing in The Sun at the height of an acrimonious national strike by the Fire Brigades Union (FBU).

He is the first public figure to suggest that the illegal technique was carried out for stories that ran in News International's best-selling daily title, rather than its Sunday red-top, the News of the World (NOTW).

One of the stories, headlined "Fire strike leader is a love cheat", appeared in The Sun during the first week of its editorship by Rebekah Brooks following her transfer from the NOTW.

As News International's chief executive, Ms Brooks, née Wade, is leading the company's defence against claims that phone hacking was rife at its headquarters in Wapping, east London.

Publicly vowing to root out wrongdoing, News International last month passed new evidence about the practice at the NOTW to the Met, prompting Acting Commissioner Tim Godwin to open a new inquiry which he said would leave "no stone unturned".

So far The Sun has been untainted by the scandal. News International said yesterday there was no evidence to support Mr Gilchrist's suspicions.

Mr Gilchrist, former general secretary of the FBU, contacted the Yard last year to ask whether his details had been logged by Glenn Mulcaire, a private detective employed by the NOTW who was jailed in 2007 for hacking the voicemails of aides to the Royal Family.

The Met told Mr Gilchrist in October 2010 that searching Mulcaire's hacking notes for his name would be problematic. But the force took a more urgent approach in a second letter to him dated 24 December, apologising for the delay and saying it would contact him with its findings as soon as possible. Mr Gilchrist is waiting to hear its response.

He told The Independent he had strong suspicions that The Sun's coverage of his extramarital affair was written after his voicemails were accessed during a long pay dispute in 2002 and 2003 which led to a strike.

In a strident campaign, The Sun criticised him for leading the strike, which resulted in soldiers being drafted in to cover in the run-up to the Iraq War.

"I have no doubt that during the 2002 and 2003 dispute I was the subject of a considerable amount of newspaper skulduggery," Mr Gilchrist said.

"It was a highly politically-charged situation at the time, very personal, and I have well-founded suspicions that information was obtained from my voicemails that led to stories in The Sun about my private and professional life. I have asked the police to investigate whether my name appears on the information they hold from Mr Mulcaire and they have said they are now consulting those records."

A front page on 20 January 2003 revealed his relationship with Tracey Holland, a former firefighter in North Wales. Published six days after Ms Brooks became editor of The Sun, the article included an account of the year-long affair by Ms Holland.

Ms Holland told The Independent this week that when she was approached by The Sun, the paper already had considerable detail about her relationship with Mr Gilchrist. "When they first came to me it was made clear that they knew all about it," she said.

"They had lots of information about how long we'd been together. Messages would have been left but I don't know if that is how knowledge of us got out."

A News International spokesman said there was no substance to Mr Gilchrist's claims: "There is absolutely nothing to suggest the appearance of these articles was linked to the interception of voicemail. News International has made it clear that, if there is any evidence of wrongdoing, swift and decisive action will be taken."

Fireman who felt heat of the media

For Andy Gilchrist's pursuers in the right-wing press it was manna from heaven. The leader of striking firefighters decried in headlines as a "Flaming Idiot" had spent £817 on a sumptuous Indian meal with companions and used his union debit card to pay for it.

Critics were quick to point out that the £200-a-head meal in February 2003 at the Cinnamon Club restaurant in Westminster took place when some firefighters were accepting food hand-outs during a rancorous five-month pay dispute by the Fire Brigades Union.

It turned out, however, that although Mr Gilchrist had used his FBU Visa card to pay for the dinner, he contacted the finance department the next day and repaid the full sum within a matter of days – all before any media coverage. Rather than being a blow-out for Mr Gilchrist and union cronies, the meal was a private gathering of family and friends. Each participant refunded their share.

The story was one of a succession of "revelations" about Mr Gilchrist, the son of a merchant seaman and a dinner lady, during a bitter strike which saw him elevated to the status of socialist bogeyman. The Sun, a strident detractor, set the tone, saying he "talks and acts like a left-wing militant dinosaur from the Seventies".

Although claims that Mr Gilchrist attended a private school (he was a grammar school boy) and stayed in five-star hotels (he preferred Travelodge-style accommodation) did not stick, he was frank in his admission that he was a member of the union movement "awkward squad" that had little time for New Labour.

This made him enemies not only in the right-wing media but also the Labour government, where some senior figures took satisfaction from his discomfiture at the disclosures about his private life.

In 2005, Mr Gilchrist was ousted from the leadership of the FBU but he can look back on 17 years as a firefighter with some pride. He was hailed as a hero in 1991 when he rescued a family of three from a burning flat, entering the building four times to ensure no one was trapped.