AMP Bank made a significantly higher contribution to group earnings in the June half, after growing both loan and deposits well above system.The bank contributed A$31 million to operating earnings in the half, up from $21 million in the previous corresponding period. AMP Bank sits within AMP's biggest division, Australian contemporary wealth management. CWM earnings growth was flat. The division's operating earnings have increased from $150 million in the June half last year to $153 million in the December half, and $157 million in the latest half.At the end of June, AMP Bank had 110,000 customers, $11 billion in its mortgage book and $5.6 billion in wholesale and retail deposits.According to Australian Prudential Regulation Authority data, AMP Bank's mortgage book increased by nine per cent in the six months to June, compared with system growth of 3.4 per cent over the same period.Its retail deposit book grew by 3.3 per cent over the half, compared with system growth of 1.5 per cent.Its capital adequacy ratio at June 30 was 11.6 per cent and its Tier 1 ratio was 8.4 per cent. Arrears were 51 basis points of its loan book.The net interest margin went up from 1.3 per cent to 1.6 per cent. With higher revenue, the cost-to-income ratio fell from 40 per cent to 32 per cent.The bank completed a $940 million securitisation deal in May.