The cost of Norwich's Northern Distributor Road has rocketed by £30m - leaving council leaders with a major headache in paying for it.

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The cost of the 12.5 mile road has soared from £148.5m to £178.5m because of construction cost inflation and design changes.

And £15m might have to be taken from County Hall's highways budget, which could delay road repairs and transport schemes.

Norfolk County Council is also banking on the government agreeing to pay the remaining £15m for the road, which will now cost £14.3m for every mile if it goes ahead.

Transport secretary Patrick McLoughlin gave the 12.5-mile road, from the A1067 Fakenham Road at Attlebridge in the west to Postwick in the east, the go-ahead in June.

But the estimated £148.5m cost was based on 2013 figures and, following talks with council contractor Balfour Beatty Civils, construction cost inflation and design changes have hiked the cost by £30m.

Councillors have been summoned to an extraordinary council meeting next month to discuss how to pay.

They will be asked to agree to seek £15m from the government, with the rest coming from County Hall's environment, development and transport budget.

George Nobbs, Norfolk County Council leader, said: 'It's hugely disappointing delays beyond our control have caused increased costs and I think it's right we press government to do what's right by Norfolk and meet us halfway.'

The council admitted a raid on the transport budget would have repercussions for other road schemes and maintenance.

Tom McCabe, executive director of community and environmental services, said: 'It isn't going to be easy for a three or four year period.'

The government has already pledged £67.5m, for the section from Postwick to the A140 and £19m for the Postwick Hub part.

The council hopes a further £40m will be generated from the Community Infrastructure Levy - a tax on development.

The Department for Transport confirmed the council had approached them about the cost of the road.

The extraordinary council meeting will take place at County Hall on Wednesday, September 2.

Mr Nobbs said he expected to know whether the government would contribute more by September and added: 'If they say no, then I will have to go back to the council again and ask what they want to do.'

Cliff Jordan, leader of the Conservative opposition at County Hall agreed the government should help. He said: 'In the grand scheme of things, it's not that much money and I would call it an investment in Norwich's future. I hope the government will say yes.'

And Mr Jordan said the hiked costs could have been avoided if the Green Party and other opponents had not challenged the road so vigorously.

He said: 'They have done everything they can to prevent and delay it. I think they are to blame for the increased cost.'

But Richard Bearman, leader of the County Hall Green group, said the road had never been a good idea. He said: 'My take is if they had spent the £10m they have already spent on the scheme on better public transport, that would have been a better use of money.'

Initial work on the road is due to start in October, with full-blown construction commencing next spring.

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