Transport for London has formally opened up a bidding race for the £260 million Barking Riverside rail extension.

The 4.5 km rail line will serve London’s biggest proposed housing development as TfL seeks expressions of interest from contractors, with a formal invitation to tended expected to be launched next year.

Construction is planned to start late next year, with the new Barking Riverside station and the new line set to be fully operational by 2021.

The bidding is set to begin almost six months after TfL approved £172 million of funding for the line, which paved the way for construction to get under way on the residential scheme.

Bellway Homes was the original developer of the scheme and had planned to build 10,800 homes on the site in 1994, however a lack of transport links meant that these proposals were scrapped.

In March, TfL submitted a Transport and Works Order to the Transport Secretary, whose decision is expected later in the year.

The Barking Riverside development will result in over 10,800 new homes being built along with leisure facilities, retail outlets and a new school.

The scheme will now be developed by L&Q after the firm purchased a 51% stake in the project from Bellway Homes, while Bellway will stay as a development partner on the scheme.

As part of the deal, L&Q also agreed to commit £70 million to the construction of the Overground extension and new station.

A section 106 agreement has meant that up to 1,500 homes could be built ahead of the construction of the Overground extension, however only 800 homes have been delivered so far, according to Barking & Dagenham Council.

Val Shawcross, Deputy Mayor of London, said that the extension of the Overground will be crucial to the success of the exciting new developments at Barking Riverside, with the new station to be built alongside the 10,800 new homes.