David Brown (46) scammed thousands of pounds by setting up fake accounts in the names of investors - including family and friends - while still working for the British Transport Police (BTP).
Brown carried out the fraud by applying for insurance policies for people without their knowledge and pocketed the commission paid out by finance giants Legal and General.
He even took out policies in the names of his brother, also a serving police officer, his mother-in-law, and other work colleagues.
He had worked with the BTP since 1990 eventually becoming a £50,000 a year inspector, but in September 2009 took on a second job with Glasgow-based financial services firm Ronald H Smith & Co.
But an investigation launched after discrepancies were found in his accounts discovered 90 per cent of policies sold by him were lapsed, cancelled or had disappeared.
He was sacked in October 2011 and a police probe found 52 false policies had been submitted by him.
Brown, a married father-of-one, had been suspended from police duties as he faced the fraud allegations.
He has now appeared at Hamilton Sheriff Court where he admitted fraudulently accepting commission totalling £92,365.97 between 2010 and 2011.
He also admitted gaining £9,590.58 by applying for loans from the Scottish Police Credit union in 2013 while pretending to live at his mother’s house in Bellshill when really he was still staying in a £300,000 detached house in Motherwell.
He claimed the credit union loan was to pay for his daughter’s education and car repairs.
Depute fiscal Paula Russell told the court Brown’s crimes were discovered when customer Anna Dunne realised unauthorised payments were being lifted from her bank account.
She said: “During 2010, David Brown attended at the home of Anna Dunne following a Go Compare enquiry.
“As a result of this, policies were taken out for life and mortgage assurance in relation to her and her husband, Peter Dunne.
“Banks details, passports and wage slips were provided to the accused by the couple.
“In September 2011, Mrs Dunne noted irregularities in her bank account with a large number of direct debits being paid to Legal and General that she did not recognise.
“She contacted Legal and General, confirmed that she did not know the policyholders, had not given permission for her details to be used, and the payments were refunded.
“It was Mrs Dunne’s queries that set off the investigation.”
The court heard Brown was arrested and it was also revealed he had been made bankrupt with debts totalling £331,673 in 2013.
Prosecutors accepted not guilty pleas to three charges which alleged he lied to obtain his second job and produced false documents to gain the employment without permission of police chiefs.
They also accepted his denial of producing false information to gain promotion to rank of inspector.
Sheriff David Bicket deferred sentence until next month for reports and allowed Brown to be released on bail.