The towers high on Boris Johnson's agenda

Conservation groups and protesters are calling on the Mayor to use his powers to halt two projects - three new towers proposed for the heart of the South Bank and a high-rise block in north-east London.

The Mayor is consulted on all major development schemes and, if he wishes, can order councils to refuse planning permission.

English Heritage is leading the campaign against plans for three towers adjacent to Waterloo station, which Lambeth council has indicated it intends to approve.

Dubbed the "Three Ugly Sisters", they would stand between 20 and 33 storeys high.

English Heritage is concerned they will ruin views of Big Ben, Westminster Abbey and the Royal Festival Hall.

It has objected against the "incongruous, dominant and visually obtrusive" plans. In a letter of objection, Paddy Pugh, director of English Heritage London, said: "Commissioners were particularly concerned about the harm which would be caused to the setting and views, of and from, the Westminster World Heritage Site.

"The issues are of national importance."

Objections have also been received from Westminster council, the Westminster Society, the
Urban Initiative Authority and residents. David Hudson, project director for developer P&O Estates, said the buildings would be in keeping with the London Plan - which was approved by pro-skyscraper former mayor Ken Livingstone.

He said: "The site does not appear in any of the London picture-postcard scenes and is an important part in the first stage of the regeneration of Waterloo, benefiting several thousands of Londoners."

A Lambeth spokeswoman said the application would be decided on its merits.

She added: "In principle our administration is very supportive of the scheme in terms of the regeneration benefits it will bring to the Waterloo area and to Lambeth as a whole." The application will be decided on 23 July.

Meanwhile, protesters are fighting proposals for an 18-storey block near Walthamstow Market, Europe's longest street market.

Waltham Forest council owns the derelict site and has selected a firm, St Modwen, to redevelop it. The scheme will be submitted to council planners next month, at which time the Mayor will be consulted.

At present the tallest building in the area is just nine storeys, and a consultation report concedes the majority of residents are opposed to high-rise development.

During his election campaign, Mr Johnson said he would resist the building of skyscrapers in inappropriate locations and where there was a large body of local objectors.

Simon Munk, of action group Fight The Height, said: "We're asking Boris Johnson to stick to his election pledges on towers in the suburbs.

"This is a clear example which he should intervene to stop: an 18-storey tower in an inappropriate, low-rise area, opposed by the overwhelming majority of local residents.

"We will be watching closely to see if he delivers on his election promise."