Number 10 confirmed that the prime minister spoke to Sir Laurie Magnus, his independent ethics adviser, this morning.
It follows claims that home secretary broke the ministerial code by asking civil servants whether she could sit a private speed awareness course rather than fine for speeding last summer.
After being told that a one-to-one course without other members of the public present would not be possible, Braverman paid the fine and received three penalty points.
The prime minister refused to give the home secretary his full backing during tense exchanges with journalists yesterday.
A spokesperson for the PM today insisted he did have “full confidence” in Braverman.
He said: “He and home secretary continue to work closely on the public’s priorities, not least tackling illegal immigration.”
On Sunak’s conversation with Sir Laurie Magnus, the spokesperson said: “He spoke with his independent adviser this morning.
“The prime minister is availing himself of the information, given he returned from the G7.”
However, he would not say whether Sunak has spoken to Braverman today.
A decision on whether Sir Laurie will carry out a full investigation is expected later today.
Deputy Labour leader Angela Rayner said: “While Suella Braverman fails to answer basic questions and gives the impression she has something to hide, Rishi Sunak is once again dithering and delaying rather than taking action over yet another case of misconduct in his crumbling cabinet.
“The prime minister must order an ethics investigation to get to the bottom of this. We’ve had 13 years of the Tories defending themselves and their mates. Enough is enough.”
Lib Dem deputy chief whip Wendy Chamberlain said: “For a prime minister who promised integrity, Sunak’s silence speaks volumes.
“He has had ample time to contact his ethics advisor and announce an investigation.
“His inability to act is a clear failure of leadership. Sunak and his entire cabinet cannot keep taking the public for fools.”
Under the ministerial code, ministers are not allowed to ask civil servants to help them with personal issues.
Dave Penman, general secretary of the FDA civil servants’ union, told Sky News: “Civil servants are publicly funded. They’re paid for by you and me. They’re not there to support the personal interests of a minister.
“They don’t do their shopping, they don’t look after their children and they don’t sort out their speeding fine.
“That’s really important as well. They’re there to work for you and I.”
He added: “The question clearly is ‘Did she abuse her position?’ And what did she ask civil servants to do? The only way to clear this up is an investigation under the ministerial code.”