Spanish Border Police have not been allowing concrete mixer trucks into the tiny British-held enclave of Gibraltar since Tuesday.

The decision was taken after Spain’s Environmental Department slammed the Gibraltarian government for tipping 70 blocks of cement into the sea.

Spanish trawlers alerted Spain’s Civil Guard police last week after they spotted Gibraltarian tugboats dropping the huge concrete blocks in what they deemed was a bid to make their job more difficult, online daily Público reported on Thursday.

Gibraltar’s government responded by saying they had begun building a man-made reef in their own waters to stop incursions by Spanish fishing boats.

Check out The Local's List on ten things you didn't know about Gibraltar.

Spain’s Environment Minister Arias Cañete has issued an official complaint at Madrid’s public prosecutor office for what he considers to be an “infringement of several environmental laws" by the Gibraltar government, which in turn has “severely damaged the type of fish species available to the Spanish trawlers.”

It’s been a particularly turbulent week for Spain-Gibraltar relations after Gibraltar accused Madrid of deliberately creating delays to car traffic to and from the disputed British-held territory and Spain.

The government of Gibraltar said it deployed an ambulance to treat peoplewith medical conditions who were stuck in the queue and distributed 11,000 bottles of water for people waiting in temperatures of up to 30 degrees Celsius (86 degrees Fahrenheit).

The border delays ended on Monday after British Foreign Secretary WilliamHague phoned his Spanish counterpart Jose Manuel Margallo to express "serious concerns" at the stoppages and Britain's Foreign Office formally protested to the Spanish ambassador in London.

Gibraltar’s plans for building an artificial reef appear to be at the centre of this week’s dispute; an attack on Spain’s fishing fleet according to the Madrid government but a necessary evil in Gibraltar’s eyes.