British media have reported that when Johnson was mayor of London he failed to declare close personal links to Jennifer Arcuri, who received thousands of pounds in public business funding and places on official trade trips.
In televised interviews that aired on Sunday (November 17) and Monday (November 18), Arcuri says that Johnson has blocked contact with her despite having a close friendship in the past.
In one interview with ITV, she said she had tried to contact Johnson many times since the newspaper reports but he would not speak to her.
But Arcuri has also repeatedly refused to answer questions about whether she had an intimate relationship with Johnson, who is currently campaigning ahead of a national election on December 12.
Johnson has said everything was done with full propriety and that there was no interest to declare.
A government audit report last month ruled a decision to award a 100,000 pound grant to a company run by Arcuri was appropriate.