Alastair Campbell revealed he is to become a host on the ITV show Good Morning Britain.
The former Labour spin doctor tweeted a series of images from the GMB studios today.
He is to co-host alongside Susanna Reid from May 10-12 during Mental Health Awareness Week.
Campbell worked as Tony Blair's official spokesman during the former Labour leader's time in office.
He has made TV programmes and written extensively about his struggles with depression.
He received the Mind Champion of the Year award in May 2009 in recognition of his work to break down the stigma around mental illness.
He said today it was “weird to be wearing a suit and tie", and declared that despite hosting the show he is not the new Piers Morgan.
Morgan left GMB in March amid the fallout from his comments about Meghan Markle's interview with Oprah Winfrey.
He said he "didn't believe a word" the Duchess of Sussex said. It led to a record 57,000 complaints to regulator Ofcom, including from the duchess directly.
Morgan also stormed off mid-show during an on-air row with weatherman Alex Beresford over the Oprah broadcast.
Today, Campbell wrote: "In addition to usual news, views and interviews hoping to draw attention to MH Issues which GMB have long championed. But also keen to get stuck in on all the big political stories post May 6 elections."
He also posted on Instagram a "mid-morning ramble" about joining GMB. He said he was nervous about being out of his comfort zone.
As a journalist, he covered the launch of the show's predecessor TVAM and appeared on breakfast TV in the 80s and 90s. He said he even had discussions with the BBC in 1994 about mainstream presenting.
On his rehearsal today, he said: "I found it quite tricky with all the stuff going on in your ear but I enjoyed it. I had one of my best fights with Nigel Farage on GMB and Piers and I had some good bust-ups."
He also said he would like to interview Prime Minister Boris Johnson or Foreign Secretary Dominic Raab.
He praised Labour leader Keir Starmer’s performance at PMQs in taking Mr Johnson to task this week.
He said bringing in “swanky” furniture showed the prime minister had the wrong mindset.
Today, Mr Johnson insisted he was a fan of retailer John Lewis as he faced a probe into the controversial refurbishment.
He was asked about reports he and his fiancee Carrie Symonds rejected furnishings by the department shop left in the Number 11 flat by his predecessor Theresa May.
It comes after the British retailer appeared to mock Mr Johnson by suggesting it had something for “almost everyone" as the Electoral Commission launched an investigation into how the new look was funded.
When asked about the reports during a visit to King Solomon Academy in west London on Thursday, Mr Johnson said: “The one thing I object to in this whole farrago of nonsense is 'I love John Lewis'.
“But what I will say is what people want this government to do is focus on their priorities.”
Ms Symonds, 33, reportedly saw the lavish overhaul as necessary to rid the prime minister's residence of the "John Lewis nightmare" left behind by Mrs May, Tatler reported.
The taxpayer funds a £30,000 annual allowance but the redecoration, which reportedly involved the company Soane, co-founded by designer Lulu Lytle – stretched beyond that.
Mr Johnson said he did not believe “there is anything to see here” when asked about the Electoral Commission’s investigation, telling reporters: “What we are doing is focusing on the stuff that really matters.”