Embattled banking giant Barclays today revealed a potential £450m bill for mis-selling complex financial products to unwitting small businesses.

Stripping out the provision and other charges, the bank saw its adjusted pre-tax profits rise 13% to £4.2bn in the six months to June 30.

Barclays was one of four banks which agreed with the Financial Services Authority (FSA) to compensate customers who were mis-sold interest rate hedging products.

Also known as interest rate swaps, the complicated derivatives products may have been sold to businesses as protection - or to act as a hedge - against a rise in rates without the customer fully grasping the risks.

The half-year results report hardly touched on the recent Libor-fixing scandal that engulfed the bank and wider industry, other than to apologise again for recent events.

But the bank did reveal that four present and past senior staff, including current group finance director Chris Lucas, were subject to a new investigation by UK regulators into fees they received under deals made in 2008.