Work on the final piece of the Cabot Circus development in Bristol – two office blocks on disused land at the end of the M32 – is expected to start at the beginning of next year.

The empty land in front of the shopping centre's car park will be transformed into 20,000sqm of office space and could be finished by next summer.

The boarded-up plot will be the last portion of the Cabot Circus site to be developed, following the creation of the 150-bed Future Inns hotel in Bond Street South.

Shops, restaurants, cafes, student accommodation and homes have been created at the £500 million Cabot Circus development since 2005.

The Cabot Gate office development in Newfoundland Street will partially conceal the 2,500-space car park.

It is being built speculatively – which means it is not being purpose-built for a tenant.

The development of the two seven-storey office buildings has already received planning permission, but developer CBRE has applied to Bristol City Council to make alterations to the original plans and slightly increase the size of the buildings.

The office site was sold by the Bristol Alliance, the developer of Cabot Circus, to Strategic Partners UK, managed by CBRE Investors, last year.

"The planning application has gone in because we have amended some of the offices on the ground floor," said Chris Grazier, of property consultants Hartnell Taylor Cook.

"The new plans are also marginally bigger, but the increase is less than five per cent of the total floor space.

"It's going to be quite an exciting looking building and we expect builders to be on site in the first part of the new year."

Kara Roderick, spokeswoman for the Bristol Alliance, said: "It will be the last piece of the development to be completed because some elements of the building work have been staggered."

A decision on the new planning application is expected to be made by Bristol City Council by early January next year.