A gang of conmen have been preying on elderly residents in a part of Leeds by demanding money for work on drains that was not needed or carried out.
In one instance one of the criminals even travelled on a bus with a victim to get money from the bank.
West Yorkshire Police said the men, working in pairs, ask householders for details including their phone number.
The gang have been targeting householders in the south Leeds area and have taken large amount of cash.
In instances where the householder has queried the work, a phone call is received, claiming to be from the workers' employer who threatens court action.
Some residents then handed over cash, but there have been reports of the offenders taking their victims to the nearest bank.
Det Insp Jim Dunkerley, of City and Holbeck CID, said: "These are extremely serious incidents where criminals have preyed on elderly people to con them out of large amounts of money.
"On some occasions have even been bold enough to escort them to the bank to ensure they get the cash.
"The reality is, if you are unaware of any works carried out at your home it is because they won't have been, and utility companies never ask for money on your doorstep.
"Utility companies always contact residents in advance of any works being carried out and will always invoice you by post.
If you have any concerns about callers at your door claiming to be utility workers, you must contact the police immediately."
Det Insp Dunkerley added: "Bank workers and the public should also look out for anyone who looks suspicious or uncomfortable when visiting the bank."