By Matt Scuffham and Steve Slater LONDON (Reuters) - Part-nationalized Royal Bank of Scotland ( RBS.L ) must address issues over its capital and future strategy before the government can start selling its shares, the new head of the agency managing Britain's bank stakes told lawmakers. James Leigh-Pemberton, who will become executive chairman of UK Financial Investments (UKFI) in January, said the outcome of new RBS Chief Executive Ross McEwan's strategic review, due in February, would be a crucial part of the investment case. "There are certain issues in relation to RBS which absolutely have to be tackled as a precursor to successful reprivatisation: sufficient capital; strategic focus on businesses where they enjoy competitive advantage and higher returns and the normalization of the capital structure," Leigh-Pemberton told parliament's Treasury Select Committee.