By Adrian Masters BBC Wales political reporter

The local newspaper adverts explained the MPs' views on major issues

The Electoral Commission said the adverts by Elfyn Llwyd, Adam Price and Hywel Williams counted as electioneering.

The local newspaper adverts were placed last April, ahead of the May poll.

The MPs say parliamentary officials had given them the go-ahead and they are confident an inquiry will clear them.

The adverts set out what the three MPs do for constituents in Meirionnydd Nant Conwy, Carmarthen East and Dinefwr, and Caernarfon, and also explain their views on major topics.

Exonerated

They state that they were paid for by the House of Commons communication allowance, which all MPs receive.

Labour MPs have complained about the timing of the move, just a week before the assembly election.

The Electoral Commission has investigated and has told Plaid that the cost of the adverts should be recorded as election expenses.

Plaid's parliamentary leader Elfyn Llwyd says he cannot talk about the matter until a separate investigation by parliament's standards commissioner has ended.