The Parliamentary Standards Commissioner is considering a complaint after it was alleged Andy Coulson failed to disclose that he was still being paid by News International when he took up his job with the Conservative Party.
Labour MP Tom Watson has complained that when Mr Coulson received a parliamentary pass, sponsored by the Prime Minister David Cameron, in September 2007, he did not declare he was receiving health insurance, a company car and severance payments from his former employers.
The rules state that anyone with a pass must declare work for which they receive more than £329 in a calendar year.
A spokeswoman for the commissioner's office said: "We have received a complaint. It's under consideration."
Mr Watson, a member of the Culture, Media and Sport Select Committee, added: "Our committee is examining the previous evidence given to it as part of the hacking inquiry.
"I am sure the Standards Commissioner will help contribute to Parliament getting to the facts of this case."
Earlier this week it emerged Mr Coulson was not asked about his severance package from News International when he took up his job as Mr Cameron's communications chief.
The disclosure by the Conservative Party raises fresh questions about the "due diligence" carried out before the ex-News of the World editor was employed.
Mr Coulson was hired by Mr Cameron in July 2007 on a reported salary of £275,000, six months after he quit as editor of the Sunday newspaper when its royal editor Clive Goodman and private investigator Glenn Mulcaire were jailed for phone hacking.
According to the BBC, for several months after he started his new role, the spin chief was still receiving instalments of money as full settlement of his two-year contract as editor of the now defunct tabloid.