The leader of Winchester City Council has dismissed top architects' fears over the redevelopment of the historic centre as "professional jealousy".

Liberal Democrat, Sheila Campbell, said: "Professional toys can be thrown out of professional prams," as the ruling cabinet discussed criticism of the Broadway-Friarsgate scheme by Winchester-based Robert Adam and Huw Thomas.

Allies and Morrison are master planners and architects for the £100m scheme on the five-acre site, which makes up around 20% of the centre.

Mr Adam and Mr Thomas fear that proposed seven-storey tower blocks could be higher than the parapet of Winchester Cathedral.

This would dramatically alter the landscape where the medieval cathedral still dominates its surroundings. No other buildings in the historic centre are this high.

The detailed designs revealing the height are not yet finished, according to the architects, but the plan is to have 364 flats, 35% of which will be "affordable".

There will also be 40 shops in new streets that reflect the medieval street pattern. The largest unit will be occupied by Sainsbury's, which will be relocating from Silver Hill.

In addition, there will be a new bus station, civic square, medical centre and car parking.

Kelsie Learney, portfolio holder for finance and resources, said: "This is going to be a huge step forward for an area that has been in decline for years and the benefits will spread out."

The scheme has already attracted controversy because London and Henley, owner of The Brooks shopping centre, says it was shut out of negotiations with the city council. But Tony Landridge, chief estates officer, said: "There was no secret deal."

In a report to cabinet, he outlined how the city council came to sign an exclusivity agreement with Thornfield in 2003 - without considering rival bids.

The council owns the freehold of King's Walk shopping centre, Friarsgate multi-storey car park, part of Marks and Spencers car park and other small parcels of land.

In the report, he said: "The first meetings with Thornfield were held in the summer of 1988. Thornfield had been introduced to the site by Stagecoach, with whom they have a number of similar joint venture relationships.

"Whilst there was knowledge of the development potential in the site and the council was approached by a small number of developers, only Thornfield followed up that approach."

Mr Langridge said negotiating with a single developer was "legally acceptable" so long as the council obtained "best consideration" for its property.

He defended the council's approach as the best way of getting a comprehensive scheme while minimising financial risk to the city. The council now plans to compulsorily purchase parts of the site not already owned by the authority, Thornfield or Stagecoach.

Conditions that have to be satisfied before development takes place include: "the granting of planning permission free from onerous conditions".

The city council is the planning authority.