The fight dates back to 2002, when Berlin’s city authorities were too broke to employ 500 police officers who had been trained in the capital, according to the Tagesspiegel on Saturday.

The then Hamburg interior senator Ronald Schill had welcomed them with open arms, promising to roll out the red carpet for them.

Now Berlin wants them back, accusing the Hamburgers of poaching their expensively-trained officers.

The Berlin senate says an agreement was made last year that 40 remaining officers would be moved back home, but that this is now being ignored and that just seven are being released.

Berlin’s police chief Dieter Glietsch has written to 21 officers giving them the chance to go back – and all have accepted, wanting to be near with their families again.

The row has provoked criticism of Gleitsch’s action from within the Berlin senate. Christian Democratic Senator Frank Henkel accused him of accepting the risk of a conflict with Hamburg, despite the fact that additional police are regularly needed in the capital during times such as May 1.

But Green Senator Benedikt Lux said, “Gleitsch is doing it brilliantly,” and suggested the same tactic be taken to try to win back teachers who have left Berlin for jobs elsewhere.