Unveiled: City high-flier

Here, seen for the first time, is London's newest landmark - a 736ft tower, designed by the Richard Rogers Partnership (RRP), for 122 Leadenhall Street in the City of London.

The proposed tower would be at least 100ft taller than any other building in the City.

Lord Rogers of Riverside, head of RRP and architectural adviser to Ken Livingstone, says that its "spire-like tapering profile" will "add to the richness of the skyline". He adds: "We are trying to find a logical shape that speaks to a more dynamic London."

But the tower faces criticism from English Heritage and conservationists, as it would appear in the background of one of the best known views of St Paul's, looking eastward down Fleet Street.

At present the dome of Sir Christopher Wren's cathedral rises alone above the surrounding buildings, with only the spire of St Martin Ludgate Hill standing in front of it.

From some points in Fleet Street the top part of Lord Rogers' building will be visible to the left of the dome.

Last year another tower in a similar but more prominent position was planned by the German-American architect Helmut Jahn. Revealed in the Evening Standard, this proposal is now being redesigned by another practice, amid fears that it will be unacceptable to planners.

The Richard Rogers Partnership, however, believes that its proposal will enhance rather than damage the view, saying the triangular shape was "a contrasting form that is not competing with the soft form of the dome".

Lord Rogers said a new public space would be created at the foot of the building. Partly enclosed by glass walls, and 90 feet high, the space would be "unlike anything in London", with "art exhibitions, music performance and cinema screenings".

The proposed tower stands opposite the Lloyds Building, which Lord Rogers completed nearly 20 years ago. The new building will revive the idea, pioneered at Lloyds, of putting lifts on the outside of the building. On the north side of the proposed tower, glass lifts will climb the full height of a coloured facade, giving vertiginous views over north London.

The 122 Leadenhall Street plan has been submitted for planning permission today and is likely to be approved by the Corporation of London, despite English Heritage objections.