A major route connecting to Princes Street in Edinburgh will be closed for almost a year for extensive utility works.

The team behind the £1bn St James Quarter development in the city's east end say the long-term closure will be the most efficient way to deal with infrastructure upgrades.

Under the plans, Leith Street will be closed for up to 44 weeks to make way for a new gas main and water drainage system six metres underground.

It is hoped the major works will ensure all the improvements are made at the same time, instead of staggered closures or partial restrictions.

The St James developers pledged the £6m works would last a maximum of 44 weeks, starting after the festival in August and ending before the event next year.

If they extend beyond that time period, a contraflow system will be put in place.

Martin Perry, director for development for TH Real Estate, said the plan had been drafted after consultation with the council, Lothian Buses and emergency services.

Some bus services will be diverted via York Place, while others will take a route along London Road.

Leith Street will still be accessible for pedestrians, cyclists and the emergency services.

Mr Perry said: "These works will allow us to reconfigure and renew the whole Leith Street corridor and help facilitate the wider regeneration of Picardy Place and the east end in a way that minimises disruption for residents, businesses and the travelling public.

"By renewing and enhancing local infrastructure as part of the Edinburgh St James scheme, we are also greatly reducing the requirement for future works and repairs, thereby minimising future disruption around the completed environment."

He added: An enhanced diversion route, with increased capacity, will be put in place for all other traffic in order to reduce congestion within the city centre, whilst access to Greenside Row and Calton Road will also be maintained for local businesses and parking."

Transport and Environment Convener Lesley Hinds, said: "St James Quarter is a hugely important development for the city, creating thousands of jobs and delivering millions of pounds to the local economy.

"But a project of this scale is bound to have an impact on the local area during construction, which is why we have been working closely with the developer to manage this as best we can."

Ms Hinds added: "A report outlining the plans will be considered by the transport and environment committee on March 21.

"Whatever plan is finally agreed, the council will continue to work very closely with the developer to monitor the impact of this work and to ensure they keep the public properly informed throughout."