Grown-up Lego fans are spitting bricks after being banned from visiting Melbourne's new construction toy mecca.

Chadstone shopping centre's Legoland Discovery Centre, the first of its kind in the southern hemisphere, opened on Tuesday.

But some adult fans who had been eagerly awaiting opening day were left disappointed when they discovered they would not be let in unless accompanied by a child.

The centre is designed for children aged between 3 and 10, and management says it is simply not suitable for adults. But some blockheads are fuming that their pre-purchased annual tickets are now worthless.