The former One Direction star, 26, was romantically linked to 49-year-old Campbell in early 2019, after attending a Davido concert together in London, where Payne was later spotted outside the fashion icon's apartment.
They fuelled the gossip by sharing flirty messages via social media following a joint trip to Ghana, but at the time, the British beauty shut down interviewers as they attempted to get to the bottom of the tabloid speculation, insisting she "never" discusses her personal life in the press.
Now Payne has taken her lead by skipping over the question during an appearance on late night U.S. talk show "Watch What Happens Live" on Thursday, December 19.
The "Strip That Down" hitmaker was put in the hot seat by host Andy Cohen during a round of the game "Plead the Fifth", in which guests are only allowed to pass on one of a series of probing questions.
After Cohen noted the pair had been spotted together back in January (2019) and had left "sexy comments on each other's Instagram pages", Payne quickly declared he would, "Plead the fifth," before giving a sly smile as he stroked his chin.
His coy behaviour prompted fellow guest Lea Michele to read into his actions, which she insisted were rather telling.
"He confirmed it!" she shouted out, as Payne insisted, "I pled the fifth. It's my right as a human!"
Payne and Campbell are said to have called off their brief romance in April (2019).
The singer, who shares two-year-old son Bear with ex-girlfriend Cheryl Cole, has since moved on with model Maya Henry.