Pure "incompetence" has led to a large section of wall collapsing onto land 15ft below, only to then be left neglected for four months in a built up residential area of Falmouth, residents have claimed.

To make matters worse, one neighbour, who asked not to be named, claimed he had written to Cornwall county council, which is responsible for the upkeep of the wall in Penwerris Terrace, warning them that it was slipping in February last year.

His fears were proved correct in December last year, when the wall crashed down onto privately owned land on the terrace below. The resident claimed that, since then, the rubble had been left lying there and no repairs had been made.

The neighbour said: "As far as I'm concerned, through their incompetence that's the mess we're in now. It's the highway's path retaining wall that has collapsed."

He claimed that the wall, which is between the houses called Poop Deck and Kiln View, collapsed on December 30 last year. "I suppose, because of the water we had and the damp weather, the water got in the wall and it came down," he said.

He continued that, around two months ago, the county council wrote to residents in the terrace warning them that the road would be closed for ten days, to allow for the removal of services such as gas and electricity, before work could be begin on the wall.

Eight weeks on and the residents still have no road access to their houses and are forced to park their cars in a designated fenced-in area at the end of the terrace.

A spokesperson for Cornwall county council said: "Cornwall county council had been monitoring the 5.2m high wall at Penwerris Terrace in Falmouth since June 2006, which collapsed into privately owned land later that year, in December, after very heavy rains. Over this period the footway above the wall and land directly below had been fenced off to protect the public and the landowner. Since the collapse the road behind the wall has been closed to vehicular traffic but pedestrian access has been maintained.

"Before the wall collapsed Cornwall county council's design services identified there were numerous services in the footway: water, sewer, gas, electricity and telecoms, including fibre optics. A site investigation located the services and determined the ground conditions behind the wall. Since then design services have co-ordinated the diversion of services to the opposite side of the road away from the wall to enable strengthening works to be undertaken safely.

"CORMAC, Cornwall county council's term maintenance contractor, are on site overseeing the realignment of the services and ensuring the site is safe. Once the service diversions have been completed a sub contractor will be onsite to install temporary piling to support the road either side of the collapsed section to enable the permanent works to commence.

"A feasibility study has been undertaken to determine the most appropriate solution to the situation. This solution, a stone-faced mass concrete wall on a piled foundation, is estimated to cost £150,000."