Tangent Structures co-director Heather Rose said when the $230,000 platform was installed off the path between the Gorge and Duck Reach, its galvanised decking was screwed into the structure using cleats and screws.

However in just four days since the lookout opened, someone has ``removed some of the cleats at the far end of the railing'' so that a panel could be lifted up six millimetres.

Ms Rose said while it wasn't unsafe to walk on the platform _ as the panels were still supported by the metal bearers underneath and it could only really hurt someone if they tried to lift it and their fingers got stuck _ Tangent contractors attended the site yesterday to ensure no-one could vandalise it again.

``They will now literally weld every screw and every cleat so that no-one can go and do this again,'' she said.

She said it was ``saddening'' that someone would tamper with the wonderful tourist platform.

``It didn't occur to us that someone would actually do this . . . but at least we know now for next time,'' Ms Rose said.

Launceston City Council general manager Robert Dobrzynski said the welding had been completed by last night, but the structure had to be inspected by engineers before it could be re-opened.

The $230,000 project was officially opened last Friday by Bass Labor MHA Brian Wightman and was paid for by the state government.

An assessment of the platform was completed before the opening.