Rents rose by 0.8% compared with the previous month and were 4.4% higher than a year earlier, letting agency network LSL Property Services said.
This meant that, on average, landlords were charging nearly £30 a month more than a year ago.
London and the south-east of England saw the biggest annual rent rises.
The warm weather and long bank holiday weekends prompted potential tenants to search for homes, said the group, which owns a lettings agents network including chains such as Your Move and Reeds Rains.
This rise in demand pushed up the cost of renting to the same record level as in November 2010, LSL said.
The east of England was the only region where rents had fallen compared with a year ago, the survey suggested.
Landlords were facing a decline in property values, and the proportion of tenants in arrears leapt, with 11.8% of all UK rent unpaid or paid late by the end of April.
However, the calendar was one key reason for these late payments, according to LSL estate agency managing director David Newnes.
“The final bank holiday of the month delayed many rental payments, but on top of this, thousands of tenants took advantage of the opportunity and booked holidays, which has impacted on the timely payment of rent,” he said.
“Nevertheless, despite the short-term factors, landlords need to remain especially vigilant over the medium-term. We are yet to see the true picture emerge from public sector spending cuts, and changing employment situations will hamper many tenants’ ability to meet their monthly rent cheque on time.”