David Cameron said he would give London Mayor Boris Johnson "a warm welcome" if he decides to return to Parliament.
The Prime Minister told ITV News' deputy political editor Chris Ship: "I think he's got a huge contribution to make.
"Whenever Boris wants to, he'll get a warm welcome from me".
More top news
The FBI is reopening an investigation into e-mails sent by Hillary Clinton via a personal server, its director has announced.
Former deputy prime minister is set to return to the Lib Dem's front bench, the Party's leader has confirmed.
Flowers have been laid at the scene where Jack Sheldon died