Collective Shout claims players are not allowed to wear any additional clothing beyond the two-piece lingerie sets and 'must agree to accidental nudity'.
Seven will begin broadcasting the Australian women's gridiron competition from December 14 on its male-focused digital channel 7mate, with a late-night timeslot of 10.30pm.
The LFL involves women playing the sport clad only in lingerie, heavy make-up and padding.
Seven's broadcast will follow the league through eight regular season matches and the final championship match.
In announcing the deal with the LFL on November 12, Seven's head of sport Saul Shtein said the channel was the "perfect fit" to broadcast the league, which he said had developed a major fan base in Australia.
Earlier this year, the league was rebranded from Lingerie Football League to Legends Football League. Its tag line was also changed from "True Fantasy" to "Women Of The Gridiron".
Collective Shout, a grassroots campaign movement against the sexualisation of women, says Seven should not be broadcasting the series.
The group has written a letter to Mr Shtein, Seven chairman Kerry Stokes and a number of other executives, asking them not to broadcast the LFL.
So far, the petition has gained almost 2500 signatures.
"The Lingerie Football League is sexist and demeaning to all women. It is not a sport, its purpose is to objectify women," the letter reads.
"We ask you also to consider the message the Lingerie Football League sends about female athletes and women in general - that their value lies not in their skills and abilities, but in their sex appeal."
Collective Shout claims players are not allowed to wear any additional clothing beyond the two-piece lingerie sets and "must agree to accidental nudity."
Caitlin Roper, Collective Shout's WA's state co-ordinator, says the broadcast undermines the achievement of female athletes in other sports, who struggle for sponsorship and media coverage.
"Seven has an opportunity to broadcast women's sport here and what they've done is rather than give those opportunities to legitimate women’s leagues, they've chosen to get behind the LFL," she said.
"That's sending a really irresponsible message and it's a slap in the face to those women and sports.
"It's not right."
The league was last broadcast on Foxtel's Fuel TV channel.
Seven group chief of corporate and regulatory affairs Bridget Fair said the network did not believe the LFL breached Commercial Television Industry Code of Practice.
"... we are satisfied that the relevant broadcast will comply with our regulatory requirements," she said in a letter.
"As with all programs Seven appreciates that the broadcast of the Legends Football League tournament may not appeal to some viewers, but that is not to say it does not have a place on free-to-air television.
"While we understand the concerns that (Collective Shout) have raised we remain of the view that the Legends of Football League is a genuine sport and is suitable for broadcast."
The LFL on 7mate is scheduled to premiere on Saturday, December 14 at 10.30pm