According to the company performance data on meeting developer services targets, published by Water UK, the scores for both Dee Valley and Portsmouth slipped one percentage point to 99 per cent.
Four water companies scored below the industry average – Wessex Water, South Staffordshire Water, Northumbrian Water and Affinity Water.
For the third time in a row Affinity Water was the worst performer with a score of 74 per cent, but also showed the biggest improvement since Q2 (October to December).
On the sewerage services side, both Yorkshire Water and Welsh Water achieved perfect scores, while United Utilities, South West Water and Southern Water received 99 per cent.
Overall the average rating for meeting the developer targets for water services was 96 per cent, an improvement on 93 per cent in Q2. For sewerage services the average score increased from 97 per cent in Q2 to 98 per cent in Q3.
Water UK chief executive Michael Roberts said: “Water companies recognise the importance of providing developers with speedy responses to their infrastructure requests and are continually improving their performance.
“In the first nine months of monitoring we have seen a significant increase in delivery against a range of targets and deadlines with overall performance increasing from 89 per cent to 96 per cent for water supply and from 94 per cent to 98 per cent for sewerage.
“This is a tangible demonstration of the industry’s contribution to the government’s commitment to speed up house building across the UK.”