The TaxPayers' Alliance has raised questions over why a House of Commons watchdog allowed an MP to claim a poppy wreath on expenses.
Labour backbencher Sarah Champion said she would repay the £17 after admitting the claim on Remembrance Day last year should "never have been made".
The claim was paid by the Independent Parliamentary Standards Authority (Ipsa) despite reimbursement for such items being banned under the rules.
TaxPayers' Alliance chief executive Jonathan Isaby said: "Taxpayers will be pleased that the money is to be repaid, as it clearly should be. The real question is why Ipsa approved the payment in the first place.
"We need to look at reforming Ipsa and the expenses system more broadly, as the changes made in light of the expenses scandal have done little to restore the public's confidence."
The details emerged in the latest run of MPs' expenses released by the watchdog last week.
Miss Champion was elected in 2012 and featured in the BBC's Inside the Commons documentary.