The three-year reign of Ian Ward as deputy leader of Birmingham City Council’s Labour group, is under threat from a colleague who decided to pull out of last week’s local authority elections and then changed her mind at the last minute.

Cath Grundy, who denied having ambitions for high office when she was at the centre of a reselection row in Kingstanding, will stand against Coun Ward for the deputy leadership at a group meeting this Saturday.

She is the only challenger and her nomination is already being seen as a direct threat to Sir Albert Bore, who has been Labour leader since 1999.

Coun Ward (Lab Shard End) is a close ally of Sir Albert and has been his deputy since May 2005, but the balance of power in the depleted 36-strong Labour group following the May 1 elections is unpredictable.

After declaring her intention at the end of March not to seek re-election in Kingstanding Coun Grundy found herself accused of leading a plot to challenge Sir Albert for the Labour leadership.

She denied any involvement, adding that her reluctance to stand again was driven by pressure of work outside of the council.

Attempts were made to have her replaced by Andy Howell, a former deputy Labour leader who found himself forced out of the group after leading a failed coup against Sir Albert in 2003. But Howell’s selection was blocked by Labour’s regional selection panel.

With less than an hour to go before nominations for election candidates closed, Coun Grundy changed her mind and agreed to be Labour’s candidate in Kingstanding.

She narrowly beat 18-year-old Tory Gary Sambrook, with an 80-vote majority, in a close battle which resulted in a 10 per cent swing to the Conservatives.

Kingstanding Labour Party chairman Hugh McCallion insisted the challenge to Coun Ward should not be seen as divisive.

Mr McCallion, himself a former deputy council leader, said: "If you go back into the history of the Labour group, positions such as leader and deputy leader were always challenged. By and large this is a healthy thing.

"Cath Grundy is a caring and hard working person who is in local government for the right reasons. She is a grafter and very bright.

"She stood for re-election and has obviously decided to come back on the council and go for it full bloodedly. It is no more than I would expect."

But one Labour insider, who declined to be named, predicted that Coun Grundy would suffer a huge defeat at the annual group meeting.

He said: "A couple of weeks ago she was trying to leave the Labour group and had to be wrestled back in. Now she want to be deputy leader.

"It’s hardly a credible act."

Coun Ward was unavailable for comment.