Official data released this week by the Scottish Government showed that local planning authorities north of the border took an average of 37 weeks to rule on 246 major applications in 2016/17.
This was up from 31 weeks in the previous year.
Major developments include applications for developments of 50 or more homes, as well as other applications covering areas such as minerals, business and industry, waste management, electricity generation and fish farming.
Major housing applications were decided in an average of 44.9 weeks, more than four weeks slower than the previous year when the average was 40.6 weeks.
The only major developments bucking the trend were minerals schemes, which were decided in an average of 30 compared to 33.6 weeks, and waste management applications, which took 18.6 compared to 22.4 weeks.
The total number of mineral decisions in 2016/17 was five, compared to 16 the previous year, and there were three waste management decisions, compared to nine the year before.
The overall decision time for major schemes has never been slower since the figures were first collected in 2012/13.
But Scotland's chief statistician, Roger Halliday, wrote in his report published yesterday, that "average figures based on a relatively small number of major development applications can be skewed by a few lengthy decisions", adding that "almost 69 per cent of major applications in 2016/17 were decided in a time quicker than the average of 37 weeks."
Overall, the rate of approvals for all types of application was 94.2 per cent and the delegation rate was 95.3 per cent. These are the highest rates over the past seven years.