An Garda Síochána is going through what is thought to be its biggest ever management clear-out with around a fifth of its senior officers leaving this year.

The exodus is driven by a one-off Government severance package, with 36 top Garda managers having been accepted. This includes eight chief superintendents, 26 superintendents, one assistant commissioner, and one senior civilian.

In addition, two assistant commissioners are also retiring on mandatory age grounds, with Garda estimates suggesting that 14 other senior officers are due to leave on age grounds — five chief superintendents and nine superintendents.

It is thought that there is very little overlap between the two groups of departures, suggesting that, in total, around 50 senior officers are set to leave the organisation.

The total number at senior rank stands at 221 — 166 superintendents, 47 chief superintendents, and eight assistant commissioners —suggesting that around 20% of the senior ranks will be going this year.

Security sources said there has not been such a clear-out since the first Fianna Fáil government in 1932 or possibly since the foundation of the force in 1922.

“Even if you just take the severance numbers, around 36, that scale of turnover has never been seen before,” said one senior source.

Garda Commissioner Drew Harris chose the people under the severance package after they formally applied for it.

The deal, which has an estimated cost of around €6.5m this year, will provide the officers with six months’ salary along with the normal pension entitlements and lump-sum payments.

Half of the officers will go in April, the other half expected to go in September, with the latter group yet to be formally signed off.

The Government introduced the severance package following a recommendation in the report of the Commission on the Future of Policing in Ireland, published in September 2018.

The Government had originally set a target of some 30 senior officers to avail of the severance package.

The full details of who is taking the package have not yet been made available by Garda HQ.

Assistant Commissioner Pat Leahy, head of the Dublin Metropolitan Region, is taking the package and is due to go in April. The Cobh man was in the final shake-up for the current commissioner position in September 2018.

Two other senior assistant commissioners, Michael O’Sullivan (Security and Intelligence) and John O’Driscoll (Special Crime Operations), are leaving on mandatory retirement grounds this month and June, respectively.

All three departures are seen as major losses for the organisation.

Chief superintendents understood to be taking the severance package include Dominic Hayes (Kilkenny-Carlow), Dave Dowling (Garda National Immigration Bureau), Tom Maguire (Security and Intelligence), John O’Reilly (Cavan-Monaghan), and Lorraine Wheatley (Dublin South Central).