Spain’s Repsol, stripped of a 51 per cent stake in Argentine oil company, YPF, by the government in Buenos Aires, has written to oil majors including ExxonMobil, Chevron and ConocoPhillips warning it would sue if they try to invest in YPF or its assets.

In letters sent yesterday and seen by the Financial Times, Repsol said it would take “actions and/or legal proceedings necessary to protect our investment?.?.?.?to prevent any improper interference or unfair competition by third parties seeking to take advantage of the current circumstances to directly or indirectly acquire interests in YPF assets in which we have an interest.”

It said it could also sue companies which “profit at the expense [of Repsol]” or take any steps “prejudicing Repsol’s ability to fully defend and recover its rights”. The expropriation of YPF leaves Respol with a 6.4 per cent stake.