Flood restoration company Munters has blasted shoddy contractors for wasting up to £80m on repairs to properties damaged by last autumn's floods.

The company said up to 10% of its work in December comprised new instructions for existing household claims where the original contractor had failed to carry out repairs to a high enough standard.

If this level of poor workmanship is reflected across the £800m cost of last autumn's flood work the total amount wasted could be up to £80m.

John Ball, president of the Chartered Institute of Loss Adjusters, said he was surprised by Munters' figures.

However, Lawclub Legal Protection said it had seen a 40% increase in calls relating to disputes over property and building matters in January.

Munters' director Tim Hawkin said bad repairs had increased the misery of flooded householders: “Even now, three months after the floods, more than 5% of new instructions we receive are a result of faulty workmanship.”

He warned that the industry could not afford to be complacent about the issue. And he added: “Lack of knowledge and experience results in under-qualified contractors carrying out shoddy and incomplete work that has to be redone, leaving the policyholder inconvenienced even further.

“You can't stop the rain, but you can reduce the cost.”

Hawkin said most poor repairs were the result of contractors not ensuring properties were sufficiently dry before starting work or failing to specify the correct redecoration materials.

In these cases Munters has had to return properties to their pre-incident condition in order to dry out properties completely before properly qualified contractors can begin work.

Geoff Williams, director of independent loss adjusters Claimex, said it used to be common practice for loss adjusters to be responsible for ensuring repair work was carried out by an able contractor. But he claimed, in some cases, insurers had chosen not to involve loss adjusters in the process and instead appointed contractors directly, increasing the scope for poor service.

This argument was, however, rejected by Norwich Union, the UK's largest insurer.

It said: “Severe flood damage warrants the involvement of either our own in-house or independent adjusters who supervise work by our own trade network, reducing the likelihood of poor repairs.”