An Bord Pleanála's rulings were successfully challenged in 63% of High Court cases last year, according to the planning body's annual report.

There were 51 legal cases decided last year and the board lost 32.

In 19 cases the High Court quashed the planning permission while in 13 cases the board admitted to defects in its decision-making process.

Only 11 decisions were upheld while another eight were discontinued or withdrawn.

Many of the challenges were against permissions granted for large-scale housing schemes under Strategic Housing Development (SHD) process.

The report reveals that Dublin had the majority of the country's SHD decisions last year.

A total of 53% of the 137 SHD rulings made by the board in 2020 were in Dublin city and county.

There were 72 cases decided in Dublin with 29 in the city area, 16 in Dún Laoghaire–Rathdown, 15 in Fingal and 12 in South Dublin.

There were 12 in Cork city and county, 11 in Co Kildare and nine in Co Meath.

There were just five in Galway city and three in Limerick city and county.

Of the 137 cases decided, 98 were given the go-ahead, allowing construction of 25,403 residential units, 2,301 student bed spaces and 774 shared accommodation units.

Permission was refused in 28 - or 22% - of cases.

The Strategic Housing Development system was introduced as a fast-track planning process in 2017 that allowed developments of over 100 homes or 200 student bed spaces to bypass local authorities and go straight to An Bord Pleanála.

It was intended to speed up the delivery of housing, but the developments provoked opposition in many areas, with residents' groups often concerned about the concentration of one bed rental housing in the schemes.

It was announced that the SHD scheme would be phased out from 28 February next, but a spokesperson for the Department of Housing said the deadline for applications has now been brought forward to 17 December.

The spokesperson said there will be a transitional period while applications go through the system.

Overall, the board said it dealt with 2,628 cases last year which was a 12% decrease on the previous year.

The report states that the decrease in case numbers can be ascribed in part to the impact of the eight-week planning timeline extension introduced because of Covid-19 restrictions.