Don't get too much of a fright if you see a string of underwear hanging from a Christchurch bridge this morning.

Eastern suburbs residents are holding a rather cheeky protest, because they are unhappy with council planning for projected rises in sea levels over the next 50 to 100 years.

They say it will leave thousands of properties at threat from flooding.

Warren Hawke from New Brighton Pier and Foreshore said they feel 'undie-supported' and 'undie-protected', hence the undie protest, so they will hang underwear from the South New Brighton Bridge.

"Were going to walk up onto the bridge, we're hanging ropes along the bridge and we're hanging signs and clean old undies, just to make our point."

People are welcome to join in, but just underlining that point - they only want CLEAN undies.