Story highlights FlynnIntel Group received $530,000 in payments from a Turkish-owned company

The work came at the height of the US presidential campaign

(CNN) The White House acknowledged Friday that President Donald Trump's transition team was aware that retired Lt. Gen. Michael Flynn engaged in work that would likely require him to register his consulting firm as a foreign agent before Flynn was tapped to serve as national security adviser.

White House press secretary Sean Spicer said Friday that Flynn's attorney contacted a Trump transition attorney to notify the transition of the potential filing, but said Trump was not made aware. Separately, Vice President Mike Pence, who headed up the transition, was notified in a November letter from the top Democrat on the House oversight committee that Flynn's firm had lobbied on behalf of a foreign power.

Spicer rejected questions about whether the disclosures should have raised red flags about Flynn, saying "it's not a question of raising a red flag."

But Flynn's Justice Department filing, which revealed that Flynn's firm worked on behalf of a Turkish-owned company to improve US confidence in Turkey's business climate, raised further questions about Flynn, who was forced to resign from his role as national security adviser last month.

Flynn's resignation came after a report alleged that he had discussed US-imposed sanctions against Russia with the Russian ambassador to the US during the transition and failed to disclose that part of his conversation to Pence. Flynn maintains he doesn't remember discussing the sanctions and Russian officials deny that the topic came up.