Image copyright Getty Images Image caption Cabinet Office minister Brooks Newmark resigned after tabloid allegations he behaved inappropriately

An MP has made make a formal complaint against the Sunday Mirror over a story that led to the resignation of a government minister.

Conservative Mark Pritchard said "questionable techniques" were involved in the paper's report that Brooks Newmark sent explicit pictures of himself to an undercover journalist.

Mr Newmark resigned after the sting, saying he had been a "complete fool".

The Sunday Mirror said that the story was in the public interest.

The paper said it had made contact with Mr Newmark during the course of an investigation into inappropriate use of social media by MPs.

'Swapped images'

Adopting the false identity of "Sophie Wittams", a male freelance reporter described himself on Twitter as a "twenty-something Tory PR girl".

"Sophie" then contacted and interacted with a number of Conservative MPs, including Mr Pritchard, via the social networking site.

The Twitter account has since been deleted, although some of the reporter's activity is still available online.

Image caption Mark Pritchard, Conservative MP for The Wrekin, said it would be the new press complaints body's "first real test"

BBC political correspondent Iain Watson said there was no evidence that any MP, apart from Mr Newmark, had acted inappropriately in response to the flattering messages sent to them from the fictional Ms Wittams.

In its account of the online exchanges between the reporter and Mr Newmark, the Sunday Mirror said the pair "swapped sexually explicit images".

Mr Pritchard, MP for The Wrekin, in Shropshire, told the BBC he would be writing a "formal complaint" to the Independent Press Standards Organisation (IPSO) "about the Sunday Mirror's questionable techniques".

Media playback is unsupported on your device Media caption Kevin Maguire, Mirror associate editor, is challenged over the coverage of a Brooks Newmark photograph

"It is in the public interest that their actions are fully investigated," he said.

"This is the first real test as to whether the new body, IPSO, has any teeth."

'Serious questions'

John Whittingdale, the Tory MP who chairs the Commons culture and media committee, said the paper had "serious questions" to answer about its journalistic techniques and it was right that the new press regulator got involved.

"Brooks (Newmark) was a fool but it does raise serious questions over whether it was a legitimate use of subterfuge. There are very clear rules.

"On first sight I am not convinced this is justified."

IPSO came into being earlier this month, replacing the defunct Press Complaints Commission.

Media playback is unsupported on your device Media caption Brian Cathcart from campaign group Hacked Off said the Sunday Mirror had "a lot of questions to answer"

It was set up by most major newspapers, including the Mirror titles, to investigate complaints from the public in the wake of phone hacking and the Leveson inquiry into the practices and ethics of the industry.

Its editors' code of practice states: "Engaging in misrepresentation or subterfuge, including by agents or intermediaries, can generally be justified only in the public interest and then only when the material cannot be obtained by other means."

Asked whether he thought the newspaper's actions were justified, Culture Secretary Sajid Javid told BBC Radio 4's PM programme that it would be "wholly wrong" for him to comment on the case as the minister responsible for media policy.

He cited "rumours that some of the people involved may be taking some legal action" as one of the reasons why it was "inappropriate" for him to give an opinion.

On IPSO's role, he added: "It is independent. It has been created by the press. Let see how it handles this. A lot of people will be watching."

'Not fishing'

Kevin Maguire, the associated editor of the Mirror, defended the story and denied that it was a result of a "fishing expedition".

The reporter concerned, he told Daily Politics, was investigating claims that half a dozen MPs were using social media to "meet people in an inappropriate way".

"There is a huge question of judgement when you have a 56-year old father of five sending lewd pictures to someone who he believes is a 21-year old woman," he said.

"As a parent, if I thought a minister... a man in a responsible position was chasing young women like this, I would think that is a matter of public interest."

A spokesman for IPSO told the Daily Telegraph newspaper: "We will consider any complaints about the story that are submitted."