Architects behind the project, BDP, have submitted plans for the redevelopment to Glasgow City Council on behalf of site owner Land Securities.

Last week it was reported that Lend Lease is being lined up as main contractor.

Land Securities, which today posted its results for the six months ending September 30, said work on the 500,000 square foot Buchanan Galleries extension is set to conclude in March 2018 at the earliest and the £300 million project will add 42 retail and catering units and a Showcase Cinema to the Galleries.

It will increase the size of the centre to about 1.2m square feet and the company said it is working on the “final details” of its plans for the development as well as that of its Westgate centre in Oxford.

The business said pre-tax profit almost tripled in the period to reach £1 billion, from £397.9m 12 months previously, driven by a valuation surplus of £880.2m across the portfolio. It also announced a dividend of 15.8 pence per share, up from 15.2p in the year-ago period.

Chief executive Robert Noel described the firm’s financial performance as “strong” and said it improved the quality of its shopping centre portfolio. Land Securities’ total combined portfolio market value amounted to £13.2bn at September 30.

Last month it gained full ownership of Buchanan Galleries by acquiring the remaining 50 per cent stake in the centre from Henderson Real Estate for £137.5m.

A spokesman added: “Both schemes have outline planning consent and we anticipate achieving reserved matters consent before the end of the financial year.

“We remain disciplined in evaluating which development schemes to pursue as the greater opportunity offered by development comes with greater risk.”

Also in its portfolio are The Centre and Almondvale South Retail Park in Livingston, 185-221 Buchanan Street, which includes the likes of Paperchase and Gap, and Kingsway West Retail Park in Dundee.

Mr Noel said the company’s strategy, including the transformation of its retail portfolio, is “generating good results” and the company has offloaded centres that “don’t fit” with its plan. During the six months it sold off assets in Bristol, Exeter and Sunderland, with year-to-date sales of £581.5m.

Gross rental income in the six-month period reached £321.3m, up from £312.8m, and net direct property expenditure grew to £18.8m from £16.1m.

Revenue profit hit £170m up from £156.5m and overall net income grew by £7m from the year-ago period to reach £302.4m.

Looking ahead, the firm said: “Our focus will remain on ensuring we own the best retail and leisure destinations and selling those that are not.”