LABOUR infighting stopped the party putting forward radical plans to devolve power to Northern areas, a leadership hopeful revealed.

Tristram Hunt, Labour’s education spokesman, said his party had “dithered” over giving local councils greater freedoms – fatally allowing the Conservatives to seize the agenda.

And he argued that weakness allowed the Tories to retain Northern seats at the General Election, saying: “It sure as hell helped them hold the line.”

Mr Hunt’s comments came as he announced he would not stand to succeed Ed Miliband as Labour’s leader, because he cannot win the backing of 34 fellow MPs, as the rules require.

Instead, he urged his colleagues to support Liz Kendall, widely seen as a fellow Blairite, and attacked the “disproportionate” influence of the trades unions in the contest.

In a speech in London, Mr Hunt attacked the “timid, institutionalised caution” of Labour’s election campaign, pointing to devolution as an example.

Mr Miliband pledged to devolve £30bn of spending to cities and counties – three times the sum planned by the Coalition – and allow them to retain any increase in business rate revenues.

But Ed Balls urged Northern leaders to reject a Manchester-style offer of more radical devolution, because George Osborne was demanding a cross-border ‘metro mayor’ in return.

Mr Hunt said: “The truth is that collectively we dithered - the Shadow Cabinet was not united.

“And when they devolved extra powers to a Labour council in Greater Manchester the Tories effectively stole our clothes.

“Now, the Northern Powerhouse did not exactly translate to a corresponding Northern breakthrough, but it sure as hell helped them hold the line.”

The education spokesman urged Labour to “shelve our timidity” by offering city-regions “devo-max” powers to vary business rates.

He said: “We need English councils and English cities slashing business rates, attracting inward investment, cutting red-tape and setting up their own enterprise zones.”

Since the Conservative election victory, the Chancellor has restated what an aide called his “mayors or bust” offer on devolution.

Councils in the North-East Combined Authority – which includes County Durham - are still holding out against what Newcastle’s leader described it as an “impossible hurdle”.

But he West Yorkshire Combined Authority has performed a U-turn by agreeing to “consult” on a metro mayor, who could rule as far as York.

Meanwhile, Mr Osborne is also keen to talk with the five Tees Valley councils – Darlington, Hartlepool, Middlesbrough, Redcar and Cleveland and Stockton-on-Tees.

With ex-Cabinet ministers Andy Burnham and Yvette Cooper certain to pass the threshold of 35 names, Mr Hunt said he did not want to “split” nominations and risk Ms Kendall falling short.

He said: “I haven't got the necessary numbers. I want as broad a range of candidates on the ballot as possible. And in order to do that I myself need to step back.”