The agency won 23 accounts overall, just three of which were without a pitch where there was no existing relationship. VCCP had a conversion rate of 76% and a total of 31 opportunities. Its wins included Transport for London and Canon.
Martin Jones, managing partner at AAR, said VCCP is a "well-oiled new-business machine".
He added: "They have an uncanny ability to act as a big agency when it is required, and a small boutique when this is what clients are looking for. This is very unusual, if not unique, in the agency marketplace."
The report covers pitches that were completed, with the result announced, between January and December 2016.
In second place, Abbott Mead Vickers BBDO won 12 accounts, seven of which were via competitive pitches. It had a conversion rate of 70%. The shop was in joint 30th position last year.
All other agencies in the top five showed vast improvement from 2015’s report.
Grey was the biggest faller among the 25 agencies in the table, dropping from second to 17th place after winning five pitches. However, its pitch conversion rate was stable at 71%.
Among the agencies to have taken part in a minimum of five competitive pitches, George & Dragon had the best competitive pitch conversion, rising from ninth place the previous year with a 90% success rate. The independent agency pitched for 11 accounts.
Jones added: "One conclusion that might be drawn is less is more when it comes to pitching, with those undertaking fewer pitches able to give them the time and energy required.
"However, one win or loss can make a big difference to your conversion rate, and any agency winning more than 50% of their opportunities should be happy with their efforts."
VCCP had the highest number of pitch opportunities from any source. The rest of the agencies in the top five had been ranked significantly lower in 2015. AMV rose from 25th to second place with 15 opportunities.
AMV also had the most wins without a formal pitch where there was no existing relationship, picking up five accounts. Lucky Generals was in second place with four accounts.