A public debate on the forest of proposed towers which would pierce the skylines of Britain's capital and other cities has been called for by the government's official advisers on architecture and conservation.

But the call, contained in a consultation document, was greeted with dismay by the City of London, which called it a gamble that could cost the Square Mile its leading financial position in the world, and with disappointment by the mayor of London, Ken Livingstone.

Developers are jostling to build tall towers in London, many twice the height of most existing towers, some so tall it is not certain they can be built. The craze, unparalleled since the 1960s, is spreading to the regions. The government's commission on architecture and the built environment (Cabe) is considering tower proposals for Bristol, Reading, Liverpool, Birmingham, Manchester, Leeds and Ramsgate.

The consultation paper on tall buildings, the first joint policy from Cabe and English Heritage, official guardian of the historic environment, is intended to be the basis of firm planning guidelines to be issued jointly next winter.

But it was immediately condemned by the City of London planning authority as introducing more delay and more uncertainty.

Judith Mayhew, chairwoman of the Corporation of London policy and resources committee, said: "The two things developers need most are speed and certainty. The more layers there are in the planning process, the more opinions there are and the slower and less certain it becomes. The majority of City firms are no longer British-owned.

"They are owned by overseas companies and it does not take much to discourage them from staying here."

She called the Cabe/English Heritage approach a gamble, and warned: "It makes the process less responsive to occupiers' demands and will quite likely threaten London's role as the centre of the financial world."

Mr Livingstone, who has become an enthusiast for towers, said: "I am disappointed that there was not more acknowledgement of the positive role tall buildings can play in cities, adding to their identity, enhancing the overall panorama and contributing towards higher density targets."

He is in discussion with both bodies on an interim planning policy, pending the completion next year of a London-wide planning review.

Off-the-record briefings have suggested that Mr Livingstone feels English Heritage is strangling modern architecture in London.

Sir Neil Cossons, chairman of English Heritage, said firmly: "I have had very good one-to-ones with Ken and the debate has moved on very considerably - to begin with there was a degree of mutual demonisation."

The policy paper did not even please the conservation movement. Adam Wilkinson, secretary of the campaign group Save, said: "It's neither here nor there - there are good things in it, but many things omitted, such as the impact of towers on the royal parks. The best thing you can say is that it has sparked the debate."

The policy paper welcomes towers in the right place, saying they can be "beacons of regeneration, and stimulate further investment".

But it warns: "There have been too many examples which have been unsuitably sited, poorly designed and detailed, badly built or incompetently managed."

Sir Stuart Lipton, chairman of Cabe, gave a cautious green light to more London towers, but added: "There are not going to be dozens of them. London is not going to be in our view a city of towers, nor will any other city in Britain be a city of towers."

Sir Neil warned that the bottom line for obtaining his approval would be "location, location, location". He said a tower in the wrong location must be thrown out by the planners - "even if it's a piece of world-class architecture".

John Rouse, director of Cabe - which is seen by developers and by the mayor's office as much more sympathetic to towers - said Cabe's refrain would have to be "location and quality, location and quality, location and quality".

Both bodies back a landmark tower by Sir Norman Foster, the so-called "erotic gherkin", the Swiss Re tower proposed for the heart of the City, on the site of the old Baltic Exchange destroyed by an IRA bomb.

But they are at odds over two other sites. The London Bridge Tower, designed by the world-renowned architect Renzo Piano, would reach 310 metres (1,000 ft) - reduced from the original 427 metres - over the South Bank.

The "glass needle" design is so radical nobody is sure it can actually be built. Cabe believes it could be "an exemplar" of good modern design, but English Heritage is uneasy about its impact on the listed London Bridge station and the historic streets around it.

The Heron Bishopsgate tower, which would form part of the backdrop of towers seen looking east from Waterloo Bridge to St Paul's Cathedral, would be taller than the NatWest Tower's 183 metres.

Cabe said it had no objection to the height or the site, but English Heritage strongly opposed it because of the views, and it has now been called in for public inquiry. Heron welcomed the policy paper, while pointing out that the tower met all the required criteria.

The policy was launched at New Zealand House, an 18-story tower completed in 1963 in Haymarket, a stone's throw from Trafalgar Square, and overshadowing the palatial Victorian and Edwardian clubs of Pall Mall.

The building would be highly unlikely to win planning permission today, but in 1995 it was listed grade 11 by English Heritage, whose postwar architectural expert, Elain Hawrood, described it "as London's finest 1960s office building".