AMP last night refused to comment on speculation it is actively considering an option to sell its retail banking arm.A report posted on The Australian website on Tuesday evening said AMP was mulling a sale of the business as a way of releasing capital after its deal to sell its life insurance business collapsed last month.According to the report, AMP has hired UBS to advise on a possible sale but no decision has been taken to proceed.The AMP group, which is subject to a tight blackout period ahead of its half-year profit announcement on Thursday, declined to respond to the report.Speculation that AMP Bank might be put up for sale intensified last month after an overhaul of its core technology platform was binned by group managing director, Francesco De Ferrari.For the past two years AMP Bank's senior management has been developing plans to migrate the business to a modern digital banking system.The abandonment of the upgrade stoked conjecture that the parent was no longer committed to repositioning the bank in new digital marketplaces.However, AMP Bank recently stepped up product marketing across electronic media channels in a drive for new customers.According to the latest banking data published by APRA, AMP Bank was one of only a small group of ADIs to expand its retail deposit base in June.The bank also is believed to be the only Australian ADI operating on a NTBS platform following ME's decision several years ago to migrate to a Temenos banking system.It appears to be struggling to bring new digital capability to market and has not yet indicated when it expects to deliver NPP-enabled services to customers.It faces other technical challenges over the next six months to ensure its platform is compliant with the requirements of the new open banking regime.Glenn Stafford, a director at Sydney-based bank technology consultancy, Perform Plus, said AMP Bank would probably need to move to a new banking system to support growth.He said he did not know of any other bank still using NTBS so a prospective acquirer would face having to migrate customer and product data to their own platform."NTBS is no worse than any other banking system if you're considering a migration," he said."There are some tricky database challenges but nothing that a smart migration team couldn't handle." The Australian reported that AMP might be eyeing a A$2 billion price tag for the business. AMP Bank generated pre-tax earnings of $148 million last year.That would value the bank at around 13.5 times earnings, which is a slight discount to the trading multiples of banks such as Bendigo and Bank of Queensland.