By staff reporter

The airline has warned that it intends to take legal action aimed at preventing Aer Lingus from making further contributions to its pension scheme.

With a stake of nearly 30%, Ryanair is Aer Lingus's biggest shareholder,

In an open letter to all Aer Lingus shareholders, Ryanair said it was "deeply worried" by the airline's stock exchange statement earlier in the week.

On Monday Aer Lingus said that it was in discussion with unions over how to fill a gap in its pension scheme of at least €400m, though it said it had no legal obligation to contribute.

Ryanair's letter said it intended to start legal proceedings as it had failed in its bid to hold an EGM of Aer Lingus shareholders to debate the issue.