The research, which was carried out on 2,026 people, reveals over half (53%) of tracker mortgage holders are not overpaying on their mortgage.
While 7% are letting their current account balances build up, 12% are not overpaying on their mortgage for fear that they will be charged for doing so.
Under one in five (19%) of tracker borrowers who are not overpaying are spending their monthly repayment windfall on day-to-day expenses, while 24% say are diverting these savings to pay off other debts.
David Elms, chief executive of Unbiased, said tracker and standard variable rate mortgage borrowers are missing out on an ideal opportunity to pay off their outstanding mortgage.
He added: “Such action would enable many thousands of borrowers to take years off their mortgage repayment term, or enjoy a greater level of repayment comfort down the line, should the economy take longer to recover.