SINGAPORE - At least two bloggers have apologised for posting negative comments in a Singtel marketing campaign.

Mr Xavier Ong, 20, and Ms Eunice Annabel Lim, 21, and others managed by social media marketing firm Gushcloud were allegedly asked to complain about telcos M1 and StarHub's services to promote Singtel's mobile plan for youth.

Mr Ong was first to say sorry in a lengthy blog post on Wednesday.

"I...apologise to anyone affected for posting negative comments towards M1 (while on a Singtel campaign) and not explicitly stating or revealing that I was on a campaign with Singtel," he wrote.

But he added that he had not lied, and that he had been "unhappy" with his service provider, M1.

Screen shots of Mr Ong's posts on his Twitter account criticising M1 were put up by blogger Xiaxue, whose real name is Wendy Cheng, along with what she called "leaked" documents allegedly asking bloggers to complain about the services of M1 and StarHub.

After her post on Saturday, M1 and StarHub wrote to Singtel to clarify the matter, and asked the Infocomm Development Authority of Singapore (IDA) to look into it.

Singtel and Gushcloud on Tuesday also apologised for the campaign.

On Monday, Ms Lim, 21, blogged that she had agreed to the brief because she was genuinely fed up with previous telco.

On Wednesday, she apologised.

"In my previous post, I've already explained and clarified some of the accusations made against me. But I left one very important thing out of it and that was an apology for my wrong doings," she said.

"I didn't know that the techniques used in the campaign were against the law. I thought they were fine since those deliverables mentioned in the brief were already acknowledged and agreed upon by Singtel, an established corporation that has years of expertise in working with advertising agencies," she said "All in all, I have realised my mistake and will do better next time by ensuring that all of my works are executed ethically."

IDA is investigating.