One-offs and lower margins have prompted RBS to downgrade forecasts at Lloyds, after the bank reported profits that were significantly under consensus estimates.While underlying results were broadly in line, one-off charges caused the group to deliver a pre-tax profit of £1.2bn in the first quarter, under expectations of £4.2bn.The broker has therefore cuts its earnings estimates by 36% for this year, and by around 10% for 2012 and 2013.RBS said the conclusion from Lloyds' first quarter results was "either the company is being run to fulfil a regulatory agenda or the group was looking to provide a conservative assessment of its current position before explaining how to bridge the gap between current and prospective returns at the forthcoming strategy day. We favour the latter conclusion." Therefore, the broker notes that all eyes will be on the strategy day.A 'buy' is maintained, but the target price is lower to 86p, from 95p previously.---BC