Investec has reiterated its 'buy' rating and 240p target price for UK lender Barclays, saying that investors should take full advantage of the stock's recent underperformance.The bank is to pay a £290m fine to UK and US regulators after it was found attempting to control submissions for the London Interbank Offered Rate (LIBOR) and the Euro Interbank Offered Rate (EURIBOR) to benefit the bank's interest rate derivatives traders. Analyst Ian Gordon from Investec said: "As things stand it is unclear whether Barclays 'successfully' manipulated LIBOR rates at all, and to the extent that LIBOR rates were manipulated, all available evidence suggests that culpability will be shared, and the scale of 'achieved' manipulation comparatively modest."The issue has prompted calls over the last few days from MPs for Chief Executive Officer Bob Diamond to step down and for those involved to face criminal charges. However, Diamond announced late last week that he would be staying at the group. "We urge investors to back Bob [...] Bob is going nowhere," Gordon said.Investec also said that it expects more radical action to address a "bloated" Barclays Capital (BarCap) cost base to get closer to the group's "unrealistic" return on equity aspirations: "This would help to underpin underlying operational performance.""Expects Barclays's sharp underperformance to reverse," Gordon added. The shares did just that on Monday morning, trading 3.72% higher at 168.9p by 10:49.BC