The average rent paid for a property in London now stands at £1,884, the monthly index showed.
Despite the tough market in the capital, rents are 2.5 times the UK average of £764.
Across the country, rents increased by 0.40% in the first six months of the year, as growth continues to slow.
The East Midlands and East of England have been the strongest regions so far this year, with growth of 0.95% and 0.70% respectively.
At the other end of the scale, rents in the North East fell by 0.08% in the first half of the year.
At a county level, Nottingham and Northamptonshire had the biggest increases of 1.43% and 1.25% respectively.
Landlords pass on costs
John Goodall, chief executive of Landbay, said: “While there remains a huge degree of regional variation, the overall trend has been a slowing of rents across the UK in the first half of this year.
“However, much of this has been London weighing down heavily on otherwise resilient growth across the UK.
“Now that London rents have bounced back to growth this could all be about to change.
“Wherever they’re based, landlords have had to face a myriad of challenges over the past two years, with regulatory and tax changes reshaping the sector.
“Despite this, there has been little sign of them passing on additional costs to tenants. However, with a rate rise on the horizon, meaning a rise in the cost of borrowing for landlords, we may well start to see landlords increasing rents in the coming months to stay afloat.”