A £2.5M scheme to upgrade one of the city’s “most neglected” roads will start this summer and cause motorists misery for nearly two years.

Iffley Road, one of the key roads in and out of the city, will be completely resurfaced as part of the Oxfordshire County Council project.

Campaigners and councillors have backed the need for the work, but have warned drivers they will face 70 weeks of ‘pain’.

The first phase of construction from The Plain to Henley Street is set to start in May and will take 40 weeks.

It will be followed by a further 30 weeks of work in 2012/13, taking the project to Donnington Bridge Road.

Upgrades will include a new road surface, new and remodelled pavements and two new zebra crossings close to Percy Street and Stockmore Street.

County councillors John Tanner and Saj Malik campaigned for the work to take place. Mr Tanner said: “The road is the worst main road in Oxfordshire.

“It will cause lots of pain to traffic in Oxford for two years, but will provide a decent road for the next 20 years.

“A single lane open for 40 weeks will bring traffic chaos but we realise that it is a necessity.”

Mr Malik said the project also included vital safety measures.

“The new crossings have been requested by parents at St Mary and St John Primary School,” he said.

The council said disruption is inevitable and is set to hold a series of discussions with key players, including the city’s bus companies, to minimise problems.

It said the work had to go ahead, despite chronic pressure on the authority’s highways budget, as Iffley Road is in such a poor state of repair.

Hugh Jaeger, chairman of the Bus Users UK Oxford branch, said: “I’m always worried when there are big roadworks on big bus routes.

“But Iffley Road really needs smartening up, the pavements and carriageway are really scruffy.”

The council’s cabinet member for transport Rodney Rose said the work was a top priority.

He added: “While money for this sort of work is tight at the moment, this road surface is reaching the end of its life and needs fixing as soon as possible.

“I think anybody who uses the route on a regular basis would agree this is a job that needs doing.”

Oxford Bus Company spokesman Phil Ashworth said: “We recognise the work has to be done and will be liaising with the council to keep delays to a minimum.”

The county council will launch a consultation on the scheme.

In November, it completed a £2m improvement scheme in London Road that took six months.