Southwark Council has warned residents to be wary of "dodgy" doorsteppers claiming to have spotted a problem with their home.
"Rogue traders can fraudulently gain access to your property and then invent some problem that needs urgent attention," the council cautioned in advice published online. "Don't believe such stories no matter how plausible they seem."
The consequences can be alarming.
"Incidents involving elderly people being escorted to their bank to withdraw tens of thousands of pounds aren't unusual."
A case due in court next year follows a homeowner in Dulwich speaking to a company about gutter repairs only to allegedly be told her roof required work that would cost £16,000.
Research commissioned by video doorbell maker Ring recently found that more than a fifth of respondents had noticed an increase in the number of scammers in their neighbourhood in the past year.
In fact 21 per cent of those polled knew someone who had been the victim of an attempted or suspected doorstep scam in the last 12 months, with London the fifth most targeted city.
So as scammers target the capital’s residents in their own homes, what advice is out there to keep people safe?
How to protect yourself against ‘distraction burglars’
The Metropolitan Police offers advice to protect against what it describes as “distraction burglars”.
Use your door viewer to see who’s there, and if you do open the door put the chain on first.
Always ask for ID and check it with the company before letting somebody into your home.
Use the phone number advertised online, as the number on their identity card could be fake. For a utility company, call the customer service department; close the door while you do this.
Remember that genuine callers won’t mind checks. If you feel at all unsure, schedule a time for the caller to come back when a friend or relative is there.
For pre-planned appointments with utility companies, a password scheme can be set up.
How to spot scammers
National reporting centre for fraud and cyber crime, Action Fraud, which is run out of the City of London, has guidance to protect against bogus tradespeople.
Check credentials, including a permanent business address and landline telephone number. The mobile phone numbers given on business cards are often pay-as-you-go numbers which are virtually impossible to trace.
Take control by asking the questions. Ask for references from previous customers or to see examples of their work.
Don’t sign on the spot — shop around. Get at least three written quotes to make sure you’re not being ripped off.
If in any doubt, ask the person to leave or call the Citizens Advice consumer helpline on 0808 223 1133.
If you’re suspicious, why not ask the salesman if you can take their photograph on your mobile phone? If the person is legitimate, they probably won’t mind.
Beware when filling in forms or speaking to the salesperson that you don’t reveal confidential details that a fraudster could use to assume your identity or take control of your finances.
Usually, you have a seven-day cooling off period. Think very carefully about having any work done or goods delivered during the cooling off period. You may have to pay, even if you change your mind.
Never pay for work before it has been completed, and only then if you are happy with it.
How to find reputable tradespeople
Citizens Advice warns that rogue traders can be persuasive as well as sometimes “intimidating and aggressive”.
As well as advice covered above, the charity suggests taking steps to reduce the risk of falling victim to scams at the doorstep.
Don’t engage with cold callers — politely say you don’t deal with doorstep sellers.
Don’t be pressured into agreeing to work being done — even if there is an issue you have been meaning to fix, don’t be rushed into making a decision.
Use reputable traders — if you do need work doing to your property use a trader that is recommended or deemed trustworthy. Contact your local Trading Standards to find out if they have an approved trader list.
More information about finding a reputable trader can be found on the Citizens Advice website.
How to deter rogue traders
As part of their latest warnings, Southwark Council advised residents not to answer the door to anyone they're not expecting.
"If you do, just say no," it adds. "Tell them you have a friend or relative that helps you, or that you don't need whatever you are offering and close the door. If they persist, tell them to leave or you'll call the police."
The local authority listed some common “dodgy” sales lines that scammers might use, such as: "We’re working around the corner and noticed a loose tile on your roof; we're in your area offering a special price if you agree today; I’ve just done a job for your neighbour; and we’ve got material left over from another job."
Southwark Council added: "You shouldn't be making decisions about buying goods or services on the doorstep — you won’t be able to shop around and compare quotes or prices. Remember that reputable traders are usually busy and therefore unlikely to be able to start any works immediately.”
Councillor Dora Dixon-Fyle said: “While tempting, cheap and immediate prices can lead to costly mistakes. The best advice is to avoid dealing with individuals who approach your home regarding any home or garden maintenance issues.
“Instead invest the time in researching tradesmen and choose contractors affiliated with an approved trader scheme. Locally, our trading standards team provide online advice messaging and free ‘no cold callers’ stickers to residents to deter rogue traders. Moreover, they strive to pursue criminal action whenever feasible.”