Barclays is planning to spin off a £4bn ($6.4bn) portfolio of complex credit assets as the UK bank presses ahead with a process to clean up its balance sheet and ease shareholder concerns over its investments.

The bank is looking at a deal to shift up to £4bn of the assets off its balance sheet in an echo of a similar transaction it did last month with a £12.3bn portfolio, people familiar with the matter said.

That deal involved a team of 45 Barclays staff, led by Stephen King, head of principal mortgage trading, leaving the bank. They then set up a company called C12, and took on the £12.3bn asset portfolio, codenamed Protium.

Barclays shares have jumped eightfold since their January lows, closing on Friday at 377p, but they are still trading at a discount to the bank's book value, while local rivals such as Standard Chartered and HSBC are on a substantial premium.

One factor that the bank believes has been overhanging investor sentiment is the continuing risk posed by toxic assets.

People familiar with Barclays' thinking said it was looking at two options for a sale of the £4bn of assets – either a replica of the Protium deal that would see Barclays traders leave with the portfolio, or a divestment to a third-party buyer.

The portfolio is made up of collateralised loan obligations –- instruments that repackage portfolios of loans into tranches of varying risk and return.

Buyers of such assets have been thin on the ground, with the exception of JPMorgan, which has been vacuuming up CLO portfolios over the past year. A third-party transaction might be more attractive to Barclays because CLO valuations have jumped in recent months.