Officers investigating Louise Haigh's "stolen" phone believed a photo she submitted of the handset had been taken after the alleged theft, Sky News has been told.
Two sources said after looking at metadata attached to the photo - information that often details when photos were captured - officers believed it had been taken after the date at which Ms Haigh alleged the phone had been stolen.
Sources close to Ms Haigh did not respond when approached about the allegation.
The Sheffield MP resigned as transport secretary on Friday after Sky News revealed she pleaded guilty and was convicted in 2014 in relation to an allegedly stolen phone.
The conviction is believed to relate to fraud.
The now former transport secretary claims the incident was a "genuine mistake" from which she did not benefit.
However, Sky News has spoken to three sources who say the stolen phone report was pursued by Ms Haigh for her own personal gain.
Sky News had also spoken to one source who alleged that the handset was used to call Ms Haigh's mother soon after the reported theft, but had been unable to verify the allegation.
On Thursday night, Ms Haigh said the incident arose after she was "mugged while on a night out" in 2013.
She said she reported the incident to the police and gave officers a list of items she believed had been taken - including a work mobile phone.
However, in her statement to Sky News, she said she discovered "some time later" that "the mobile in question had not been taken".
In the interim she was issued with another work phone. When she turned on the original work device, it "triggered police attention and I was asked to come in for questioning", she said.
"My solicitor advised me not to comment during that interview and I regret following that advice," she added.
"Under the advice of my solicitor I pleaded guilty - despite the fact this was a genuine mistake from which I did not make any gain.
"The magistrates accepted all of these arguments and gave me the lowest possible outcome (a discharge) available."
It is understood Ms Haigh believes she disclosed the incident in full when she was appointed to the shadow cabinet in 2020.
However, Downing Street said on Friday that Ms Haigh resigned after "new information" emerged, but declined to say officially if the prime minister knew about the conviction when he appointed his cabinet in July.
On Friday, a source told Sky News' political editor Beth Rigby that the story that emerged on Thursday was "inconsistent" with what Sir Keir had been told when Ms Haigh was appointed to his shadow cabinet.
It is understood the prime minister was "not able to square the circle" and as a result the cabinet minister was advised to resign.
Friends of Ms Haigh insist she shared the "full facts" of the conviction and that Sir Keir "had expressed sympathy that police had taken the decision to prosecute her".
(c) Sky News 2024: Louise Haigh's photo of stolen phone 'taken after alleged theft'