The architect who helped create Glasgow's Burrell Collection museum has expressed concern over its multi-million pound redevelopment.

John Meunier, one of the architects behind the building, said the redesign should not "mess around" with the original.

The building, which opened in Glasgow's Pollok Park in 1983, was designed by Mr Meunier, Barry Gasson and Brit Andresen.

The £66m restoration will expand the building's available floor space, allowing 90% of the museum's 9,000-item collection to be displayed.

Architects John McAslan + Partners won the commission to carry out the work last year.

However, Mr Meunier, who is emeritus professor of architecture at Arizona State University, said he was concerned about the redesign, especially changes to the main entrance and the Hutton Rooms, which features furnishings from Burrell's castle near Berwick on Tweed.

In a letter to the architects, Mr Meunier asked for a meeting over the planned changes.

He said: "The issue for me is the long term and whether it retains its status as one of the best 20th century works of architecture in Scotland, superbly matching the architecture to the works of art, while continuing to honour the intentions of its progenitor [William Burrell].

"For it to do that a lot more has to be retained, including the extended entry sequence of graduated spaces, and the programmatic requirement of the will that the restored Hutton Rooms be retained."

He added: "There is obviously a lot more to discuss, including the careful insertion of elevators as all three levels come into play, but my main message is to mess around with the basic, experience, logic and composition of the original building as little as possible, and to exercise architectural creativity to meet your new goals in a way that sustains the material and formal language of the original."

Paddy Pugh, director of conservation and planning at architects McAslan, said he was sorry to hear of the comments.

He wrote to Mr Meunier: "We have the utmost respect for the building and have, as you know, taken a great deal of care to understand its design intent and significance.

"There is no doubt in our minds that The Burrell fully deserves its recognition and status as a Category A listed building."

He said the "visitor and curatorial expectations of public cultural buildings" had changed significantly over the almost 40 years since the building was designed.

He added: "Glasgow Life and The Burrell Renaissance, as custodians for both the building and the Collection, are absolutely convinced that changes to the gallery and display of objects are required in order to reverse that decline.

"Beyond repairing/replacing the roofs, facades and building services, the principle architectural changes are designed to improve access into and around the building."

Glasgow Life said it had not been contacted by Mr Meunier.

It said the "original, existing entrance will remain exactly the same, open and in use at all times".

It added: "Some changes to fabric will be made to improve access into and around the building to meet current requirements for visitors but design intent, plan-form, materiality, appearance, and character, will remain substantially unchanged."