Barclays is to close down a controversial part of its business which helps clients avoid tax, the BBC understands.The bank will announce that part of its Structured Capital Markets (SCM) business will be axed as part of a wide-ranging strategic review.The announcement is expected alongside Barclays' full year results on Tuesday.The move comes as part of the bank's attempts to improve its image following a string of scandals.Barclays was fined £290m ($450m) over the Libor-rigging scandal last year, and has set aside nearly £3.5bn to cover possible payouts related to the mis-selling of payment protection insurance (PPI) and interest rate investment products.Barclays chief executive Antony Jenkins has tried to place more emphasis on the ethics of the bank's practices since taking over from his predecessor Bob Diamond, who resigned in the wake of the Libor scandal in July.Last week he told MPs he was "shredding" Mr Diamond's legacy at the bank.Mr Jenkins' strategic review of the bank, dubbed the "Transform" programme, is also expected to involve 2,000 job losses in the investment banking business. Ethics focusBarclays is expect to continue helping clients with their tax arrangements, but will not engage in activities where the main purpose is to avoid tax."There are some areas that relied on sophisticated and complex structures, where transactions were carried out with the primary objective of accessing the tax benefits," Mr Jenkins is expected to say on Tuesday."Although this was legal, going forward such activity is incompatible with our purpose. We will not engage in it again."According to insiders, the closure of the tax SCM unit marks an important and significant break with the past.At its peak it accounted for most of Barclays' investment banking revenue.Former chancellor Lord Lawson, a member of the Parliamentary Banking Commission, last week accused Barclays of being involved in legal tax avoidance on an "industrial scale".Barclays is also due to report the size of its bonus pool on Tuesday.Earlier this month Mr Jenkins waived his bonus for last year, thought to be about £1m, following what he described as a "difficult" year for Barclays, and warned that others would also be cut.