Tracy Grimshaw’s TV colleagues have paid tribute after the host of A Current Affair‘s bombshell announcement that she will stand down.

Grimshaw delivered the news of her surprise decision live on air on Monday.

She will leave in November after 17 years at the helm of Nine’s prime-time show – and is planning a long holiday.

In a message delivered where the show’s nightly promo would normally run, Grimshaw said she wanted to make the announcement on her own terms.

“I’ve decided to finish up with A Current Affair this year,” she said.

“I want you to know it’s been my decision alone and I’m not being shoved out the door by the boys club because I’m too old.

“I’m not too old, I’m just a bit tired. And for the record both the boys and the girls have asked me to stay.”

Tweet from @ACurrentAffair9

Grimshaw’s plans had been a closely held secret, with even production staff on the Nine show reportedly unaware of her decision right up until the on-air announcement.

On Tuesday morning, Today co-host Karl Stefanovic paid tribute to his long-time colleague.

“She didn’t tell me she was leaving,” he said.

When Stefanovic joined Today in 2005, Grimshaw was his co-host and mentor.

“What a legend. I started out on this show with her 18 years ago,” he said.

“She is the best in the business. I had the great fortune of working for her for a year and she was exceptional.”

Grimshaw, 62, started as a reporter with the network in Melbourne in 1981. She began presenting day-time news bulletins in 1985.

A decade later, she joined the Midday Show, co-hosting it with David Reyne before moving to Today, which she co-hosted with Steve Liebmann, in 1996.

She began as ACA host in early 2006, taking over from Ray Martin.

Tweet from @ACurrentAffair9

On Monday, Grimshaw said it was time for a change.

“I’ve basically been a shift worker for 26 years, driving to work before dawn for nine years on the Today Show, and the past 17 years driving home after dark here on A Current Affair, and it’s time for less of that daily obligation,” she said.

“It has been my privilege to host this show.

“You’ve let me indulge my love of interviewing here. I’ve talked to people who’ve made us all laugh and cry, who’ve shared their triumphs and their challenges and their wisdom and despair.”

In a statement minutes after Grimshaw’s announcement, Nine news and current affairs director Darren Wick described her as “irreplaceable”.

“She is the best interviewer on television and has been for many years,” he said.

“She will forever take her place alongside the greatest interviewers that Australian journalism has ever seen.”

On Monday night, Grimshaw thanked her audience. She said she was lucky to have held the ACA hosting role for so long.

“Thank you for your loyalty. I hope I’ve repaid it,” she said.

Nine is yet to name a replacement host for A Current Affair.