A group of architects on Saturday urged members of their industry to boycott a lecture by Prince Charles in protest at his criticisms of modern design.

In a letter published in Britain's The Guardian newspaper, nine architects urged others to shun the address Tuesday, when the Prince of Wales will speak at London's Royal Institute of British Architects.

The prince has repeatedly attacked modern design, and criticized the heavy use of steel and glass in building projects, once calling a proposed extension to Britain's National Gallery a "monstrous carbuncle on the face of a much-loved and elegant friend."

Architects say the prince's influence means more people are likely to oppose such designs when local councils decide whether or not to approve the projects.

In Britain, members of the public can raise objections to building proposals, which must be considered by planning officials in their decisions.

"His actions again threaten an important element of our democratic process," the group wrote in the letter. "To all architects who value these democratic procedures, we advocate a boycott of the prince's lecture."

Prize winning architects Will Alsop and Chris Wilkinson were among the group who put their names to the latest letter.

Last month, architects including Norman Foster, Zaha Hadid and Frank Gehry were among 10 signatories to a letter criticizing the prince after he spoke out against plans to convert a former army barracks in London into luxury homes.

The prince has criticized a modern glass and steel design being used in the development in the Chelsea district, which neighbors the Royal Chelsea Hospital, a historic building designed by Christopher Wren, 17th century architect of St. Paul's Cathedral.

A spokeswoman for the prince declined to comment Saturday on the latest letter.