The average number of mortgage cases placed by intermediaries increased to 105 a year in Q2, up from 96 in the previous quarter and the highest level recorded since Q1 2010.
Mortgage brokers reported an average of 110 cases, compared with 71 among IFAs.
The rise followed increased activity at the beginning of the year, when geopolitical uncertainty and volatility in swap rates prompted some borrowers to bring forward mortgage activity.
Volumes continued to increase in Q2, with Bank of England figures showing gross secured lending rose by £9bn during the quarter to £77bn.
Intermediaries dealt with an average of 29 decisions in principle during Q2, up from 26 in Q1, while the proportion that resulted in a completion increased from 37% to 40%. This meant around 11 of every 29 DIPs progressed to completion.
The proportion of accepted DIPs progressing to a full mortgage application also increased, from 73% to 78%, marking the first quarterly rise in a year.
Meanwhile, the proportion of full applications resulting in an offer increased from 84% to 87%, while the overall application to completion conversion rate remained unchanged at 61%.
Intermediaries focused on first time buyers recorded a 10 percentage point increase in DIP to completion conversion, from 29% in Q1 to 39% in Q2.
Despite higher business volumes and improved conversion rates, confidence in the wider market declined during the quarter.
Net confidence in the mortgage industry fell 13 points to 66, while confidence in the intermediary sector dropped 12 points to 70. Confidence in advisers' own businesses fell seven points to 88.
Kate Davies, executive director of IMLA, said: "The most striking feature of these figures is the contrast between sentiment and activity. Intermediaries’ confidence has fallen but they are busier than ever, and conversion rates are improving.
"The fall in confidence is understandable given the unsettled economic and political backdrop. The conflict in the Middle East has pushed up energy prices and inflation expectations, reducing hopes of further cuts to Bank Rate this year, although the economic impact has so far proved less severe than initially feared. At home, another period of political uncertainty culminated in our seventh change of Prime Minister in a decade.
"Against that backdrop, the resilience of the mortgage market is encouraging. Andy Burnham has arrived in Downing Street on a wave of optimism and with an ambition to get the economy moving. It will be interesting to see whether that more positive mood feeds through into intermediary confidence in Q3."
