Brooks Newmark, a lawmaker in Prime Minister David Cameron's Conservative party and a married father of five children, stepped down on Saturday after the Sunday Mirror tabloid said he had sent an explicit photo to an undercover reporter.
The reporter had posed as a pretty blonde party activist and flirted online with the 56-year-old politician, who had led efforts to get more female Tories elected to parliament.
"Test for IPSO and Met Police. I will write to both today about Sunday Mirror story. Was the criminal law and IPSO Code of Conduct broken?" Pritchard tweeted.
IPSO was set up to replace the Press Complaints Commission (PCC), which was discredited after the revelation of widespread phone-hacking at the News of the World tabloid.
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It only started work this month but critics already question how effective it can be given that, like the PCC, it involves members of the press regulating themselves.
"The investigation, which had a clear public interest, was carried out following information from a reliable source," the paper's weekend editor, Alison Phillips, told the Guardian newspaper.
However, media commentator Roy Greenslade, a professor of journalism at City University in London and a former editor of the Daily Mirror, disagreed.
He noted that so-called "fishing expeditions" -- when subterfuge is used on the off-chance of discovering some wrongdoing -- are not allowed under the Code of Conduct unless there are existing grounds for the investigation and it is "in the public interest".
He added of Newmark: "He hadn't broken the law, it was an adult to adult piece of foolishness. I can't see that this really advanced investigative journalism in any way."
It also emerged today that the photograph on the fake Twitter account used to communicate with the politician was of a Swedish model, who had not given her permission.
"I feel shocked. It's unpleasant that someone used the picture like that without permission," 22-year-old Malin Sahlen told Swedish tabloid Aftonbladet.