Investec has downgraded its recommendation for Lloyds Banking Group from 'hold' to 'sell' and left its target price at 50p following the bank's first-quarter results this week."After many happy hours tinkering with our forecasts, our view remains substantially unchanged," said analyst Ian Gordon.However, he said that after an exceptionals-enhanced attributable profit of £1.5bn in the first three months of the year, Investec's forecasts for £0.2bn in the second quarter and just £0.1bn in both the third and the fourth "do appear deeply underwhelming!"The broker highlighted last week's "truly dreadful" data on mortgage lending which showed that lending was down sharply in March following a weak February. Although Lloyds and other banks may get some support from the government's 'Help to Buy' scheme in 2014, Gordon said it remains a "tough macro backdrop".While Investec believes that the muted outlook for revenues and returns is the primary constraint to the stock's valuation, Gordon did highlight some positives surrounding Lloyds and said that his stance remains "solidly constructive"."We welcome the collapse of the cut-price disposal to the Co-op, we are positive on both the Spanish divestment, and more broadly, the encouraging pace of Non-Core run-off. We do not share the Financial Policy Committee's concerns in relation to Lloyds' capital position, albeit we acknowledge that a first dividend my not be declared before February 2015. "Lloyds is clearly travelling in the right direction, but much further patience is required."The stock was down 0.85% at 53.74p by 10:39.BC