Plans to build the tallest skyscraper in the City of London have been unveiled by Eric Parry Architects, who say it will feature the UK’s highest free public viewing gallery.

At a height of 309.6m (1,000ft), Parry’s commercial tower, named 1 Undershaft, will be as tall as its Renzo Piano-designed neighbour The Shard – currently the tallest building in western Europe. It will be located in the heart of the capital's financial district, between Norman Foster's Gherkin and the Cheesegrater tower by Rogers Stirk Harbour + Partners.

The design envisions large areas of public space at both the top and bottom of the skyscraper. A new public square will be created at the base, while the top floors – featuring a 200-capacity restaurant and educational classrooms, in addition to the gallery – will be open to the public seven days a week.

Visitors to the top will be able to see as far as 60km (37 miles) into the horizon. An educational attraction, likely to be operated by the Museum of London, will provide information about the growth and history of the capital.

The design for the new tower – commissioned by Singapore-based Aroland Holdings – visualises a simple square-shaped tower featuring huge red cross braces, white louvre cladding and special fins to reduce solar glare and keep the building cool. In total, the structure will provide more than 90,000sq m (968,750sq ft) of net internal area.

“The building represents the very best of British architecture something we hope Londoners will be very proud of,” said studio principal Eric Parry.

“It will be a building where the public are put first, reconnecting them with the city’s tall building cluster, becoming the jewel in the crown of the City of London.”

Parry’s proposal for a new large public square at the base of the tower will be realised by elevating the building’s reception lobby, creating an open space below the skyscraper itself for members of the public to walk under. In the winter, there are plans for ice rinks be installed in the space, with an open-air cinema being considered for the summer months.

The designers plan to demolish the 28-storey St Helens building, which is currently located on the site, but will retain its basement. This will be transformed into a 1,800sqm (19,300sq ft) retail space featuring new restaurants, cafes, and shops.

A planning application for the project will be submitted to the City of London in the New Year, with a final decision expected by Q2 2016. If the plans are given the green light, it will take 18 months to demolish the existing tower and up to five years to build the new one.

Aroland Holdings are working with planning consultants DP9, who have worked on the huge regeneration of Battersea Power Station, and engineering advisors WSP Parsons Brinckerhoff.

A budget for the project has not yet been released.