Ms Dorries will begin hosting a new talk show, Friday Night With Nadine, on February 3.
Lord Pickles, chair of the Advisory Committee on Business Appointments (Acoba), said she informed him of her decision on Friday.
He told her that “failing to seek and await advice” was a rule violation.
Lord Pickles recommended that “given the transparent nature” of the role, it would be “disproportionate to take any further action in this case” in a separate letter to Chancellor of the Duchy of Lancaster Oliver Dowden.
However, he added that the case was a “further illustration of how out of date the government’s rules are”.
Ms Dorries should have sought clearance from Acoba for any new employment or appointments she takes on within two years of leaving ministerial office, according to current rules.
“The risks under the rules in these types of appointments are usually limited,” Lord Pickles told Ms Dorries.
“Had you approached Acoba in good time before agreeing to the 26-week contract… we would have been able to advise you appropriately in advance,” he said.
In due course, the Cabinet Office is expected to respond to the letter.
The first hour-long weekly programme will include an exclusive interview with Boris Johnson.
Another MP, Jacob Rees-Mogg, was recently announced as a new presenter on rival news channel GB News.